[extension/googleclientauth] Add new component boilerplate scaffolding (

open-telemetry#31518)

**Description:**
This adds the basic component boilerplate following the recommendations
for PR1 in
https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/CONTRIBUTING.md#adding-new-components

**Link to tracking Issue:**
open-telemetry#31412

**Testing:** Ran various `make ...` commands as listed in docs. Ignored
generated files and failures from unrelated components.

**Documentation:** New readme and metadata (to be filled in, see
tracking issue)

---------

Co-authored-by: Curtis Robert <crobert@splunk.com>

.chloggen/gcp-auth-ext.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: new_component
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: googleclientauthextension
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add boilerplate for Google Client Auth Extension
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [31412]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

.github/CODEOWNERS

@@ -92,6 +92,7 @@ extension/encoding/jsonlogencodingextension/             @open-telemetry/collect
 extension/encoding/otlpencodingextension/                @open-telemetry/collector-contrib-approvers @dao-jun @VihasMakwana
 extension/encoding/textencodingextension/                @open-telemetry/collector-contrib-approvers @MovieStoreGuy @atoulme
 extension/encoding/zipkinencodingextension/              @open-telemetry/collector-contrib-approvers @MovieStoreGuy @dao-jun
+extension/googleclientauthextension/                     @open-telemetry/collector-contrib-approvers @aabmass @dashpole @jsuereth @punya @damemi @psx95
 extension/headerssetterextension/                        @open-telemetry/collector-contrib-approvers @jpkrohling
 extension/healthcheckextension/                          @open-telemetry/collector-contrib-approvers @jpkrohling
 extension/httpforwarderextension/                        @open-telemetry/collector-contrib-approvers @atoulme @rmfitzpatrick

.github/ISSUE_TEMPLATE/bug_report.yaml

@@ -92,6 +92,7 @@ body:
       - extension/encoding/otlpencoding
       - extension/encoding/textencoding
       - extension/encoding/zipkinencoding
+      - extension/googleclientauth
       - extension/headerssetter
       - extension/healthcheck
       - extension/httpforwarder

.github/ISSUE_TEMPLATE/feature_request.yaml

@@ -86,6 +86,7 @@ body:
       - extension/encoding/otlpencoding
       - extension/encoding/textencoding
       - extension/encoding/zipkinencoding
+      - extension/googleclientauth
       - extension/headerssetter
       - extension/healthcheck
       - extension/httpforwarder

.github/ISSUE_TEMPLATE/other.yaml

@@ -86,6 +86,7 @@ body:
       - extension/encoding/otlpencoding
       - extension/encoding/textencoding
       - extension/encoding/zipkinencoding
+      - extension/googleclientauth
       - extension/headerssetter
       - extension/healthcheck
       - extension/httpforwarder

extension/googleclientauthextension/Makefile

@@ -0,0 +1 @@
+include ../../Makefile.Common

extension/googleclientauthextension/README.md

@@ -0,0 +1,45 @@
+# Google Client Auth Extension
+<!-- status autogenerated section -->
+| Status        |           |
+| ------------- |-----------|
+| Stability     | [development]  |
+| Distributions | [] |
+| Issues        | [![Open issues](https://img.shields.io/github/issues-search/open-telemetry/opentelemetry-collector-contrib?query=is%3Aissue%20is%3Aopen%20label%3Aextension%2Fgoogleclientauth%20&label=open&color=orange&logo=opentelemetry)](https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aopen+is%3Aissue+label%3Aextension%2Fgoogleclientauth) [![Closed issues](https://img.shields.io/github/issues-search/open-telemetry/opentelemetry-collector-contrib?query=is%3Aissue%20is%3Aclosed%20label%3Aextension%2Fgoogleclientauth%20&label=closed&color=blue&logo=opentelemetry)](https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aclosed+is%3Aissue+label%3Aextension%2Fgoogleclientauth) |
+| [Code Owners](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/CONTRIBUTING.md#becoming-a-code-owner)    | [@dashpole](https://www.github.com/dashpole), [@damemi](https://www.github.com/damemi), [@aabmass](https://www.github.com/aabmass), [@jsuereth](https://www.github.com/jsuereth), [@punya](https://www.github.com/punya), [@psx95](https://www.github.com/psx95) |
+
+[development]: https://github.com/open-telemetry/opentelemetry-collector#development
+<!-- end autogenerated section -->
+
+This extension provides Google OAuth2 Client Credentials and Metadata for gRPC and http based exporters.
+
+## Configuration
+
+```yaml
+extensions:
+  googleclientauth:
+
+receivers:
+  otlp:
+    protocols:
+      grpc:
+
+exporters:
+  otlp/withauth:
+    endpoint: 0.0.0.0:5000
+    ca_file: /tmp/certs/ca.pem
+    auth:
+      authenticator: googleclientauth
+
+service:
+  extensions: [googleclientauth]
+  pipelines:
+    metrics:
+      receivers: [otlp]
+      processors: []
+      exporters: [otlp/withauth]
+```
+
+The following optional config fields are available:
+- `project` - The Google Cloud Project telemetry is sent to if the `gcp.project.id` resource attribute is not set. If unspecified, this is determined using application default credentials.
+- `scopes` - The oauth 2.0 [scopes](https://datatracker.ietf.org/doc/html/rfc6749#section-3.3) requested by the extension.
+- `quota_project` - The [project](https://cloud.google.com/apis/docs/system-parameters) for quota and billing purposes. The caller must have `serviceusage.services.use` permission on the project.

extension/googleclientauthextension/config.go

@@ -0,0 +1,12 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package googleclientauthextension // import "github.com/open-telemetry/opentelemetry-collector-contrib/extension/googleclientauthextension"
+
+// Config defines configuration for the Google client auth extension.
+type Config struct {
+}
+
+func (cfg *Config) Validate() error {
+	return nil
+}

extension/googleclientauthextension/doc.go

@@ -0,0 +1,7 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+//go:generate mdatagen metadata.yaml
+
+// Package googleclientauthextension implements an extension that provides authentication with Google Cloud.
+package googleclientauthextension // import "github.com/open-telemetry/opentelemetry-collector-contrib/extension/googleclientauthextension"

extension/googleclientauthextension/factory.go

@@ -0,0 +1,27 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+//go:generate mdatagen metadata.yaml
+
+package googleclientauthextension // import "github.com/open-telemetry/opentelemetry-collector-contrib/extension/googleclientauthextension"
+
+import (
+	"context"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/extension"
+	"go.opentelemetry.io/collector/extension/auth"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/extension/googleclientauthextension/internal/metadata"
+)
+
+func NewFactory() extension.Factory {
+	return extension.NewFactory(
+		metadata.Type,
+		func() component.Config { return &Config{} },
+		func(context.Context, extension.CreateSettings, component.Config) (extension.Extension, error) {
+			return auth.NewClient(), nil
+		},
+		metadata.ExtensionStability,
+	)
+}

extension/googleclientauthextension/go.mod

@@ -0,0 +1,52 @@
+module github.com/open-telemetry/opentelemetry-collector-contrib/extension/googleclientauthextension
+
+go 1.21
+
+exclude github.com/knadh/koanf v1.5.0
+
+require (
+	github.com/stretchr/testify v1.9.0
+	go.opentelemetry.io/collector/component v0.96.1-0.20240306115632-b2693620eff6
+	go.opentelemetry.io/collector/confmap v0.96.1-0.20240306115632-b2693620eff6
+	go.opentelemetry.io/collector/extension v0.96.1-0.20240306115632-b2693620eff6
+	go.opentelemetry.io/collector/extension/auth v0.96.1-0.20240306115632-b2693620eff6
+	go.opentelemetry.io/otel/metric v1.24.0
+	go.opentelemetry.io/otel/trace v1.24.0
+	go.uber.org/goleak v1.3.0
+)
+
+require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.2.0 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/go-logr/logr v1.4.1 // indirect
+	github.com/go-logr/stdr v1.2.2 // indirect
+	github.com/go-viper/mapstructure/v2 v2.0.0-alpha.1 // indirect
+	github.com/gogo/protobuf v1.3.2 // indirect
+	github.com/golang/protobuf v1.5.3 // indirect
+	github.com/knadh/koanf/maps v0.1.1 // indirect
+	github.com/knadh/koanf/providers/confmap v0.1.0 // indirect
+	github.com/knadh/koanf/v2 v2.1.0 // indirect
+	github.com/mitchellh/copystructure v1.2.0 // indirect
+	github.com/mitchellh/reflectwalk v1.0.2 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/prometheus/client_golang v1.19.0 // indirect
+	github.com/prometheus/client_model v0.6.0 // indirect
+	github.com/prometheus/common v0.48.0 // indirect
+	github.com/prometheus/procfs v0.12.0 // indirect
+	go.opentelemetry.io/collector/config/configtelemetry v0.96.1-0.20240306115632-b2693620eff6 // indirect
+	go.opentelemetry.io/collector/pdata v1.3.1-0.20240306115632-b2693620eff6 // indirect
+	go.opentelemetry.io/otel v1.24.0 // indirect
+	go.opentelemetry.io/otel/exporters/prometheus v0.46.0 // indirect
+	go.opentelemetry.io/otel/sdk v1.24.0 // indirect
+	go.opentelemetry.io/otel/sdk/metric v1.24.0 // indirect
+	go.uber.org/multierr v1.11.0 // indirect
+	go.uber.org/zap v1.27.0 // indirect
+	golang.org/x/net v0.20.0 // indirect
+	golang.org/x/sys v0.17.0 // indirect
+	golang.org/x/text v0.14.0 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20240123012728-ef4313101c80 // indirect
+	google.golang.org/grpc v1.62.1 // indirect
+	google.golang.org/protobuf v1.33.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)