opentelemetry tracer: add support for environment resource detector

[joaopgrassi]

Commit Message: Allow specifying resource detectors for the OpenTelemetry tracer via a new configuration resource_detectors. The resource detector reads from the env variable OTEL_RESOURCE_ATTRIBUTES which is defined by the OTel specification. The detector returns a resource object populated with the detected attributes, which is sent as part of the OTLP request.

Additional Description: This PR adds the "foundation" for building other resource detectors in Envoy. It is based on the OTel collector implementation. Users can configure multiple resource detectors, and they work together to "merge" all the detected attributes into a single resource object, which is then part of the OTLP message exported.

Risk Level: Low

Testing: Multiple unit tests, that cover all new code/scenarios. I also did manual testing, running Envoy locally with the OTel tracer + env resource detector enabled. Resource attributes detected from my environment is successfully exported as seen in the Jaeger screenshot.

Docs Changes: Not sure if I should add/where. Happy to do it.
Release Notes: N/A
Platform Specific Features: N/A
[Optional Runtime guard:] N/A
[Optional Fixes #28929]

Here is how the new config is used:

tracing:
  provider:
    name: envoy.tracers.opentelemetry
    typed_config:
      "@type": type.googleapis.com/envoy.config.trace.v3.OpenTelemetryConfig
       grpc_service:
         envoy_grpc:
           cluster_name: opentelemetry_collector
         timeout: 0.250s
       service_name: envoy-gRPC-exporter
       resource_detectors: # --> NEW CONFIG
         - name: envoy.tracers.opentelemetry.resource_detectors.environment
           typed_config:
             "@type": type.googleapis.com/envoy.extensions.tracers.opentelemetry.resource_detectors.v3.EnvironmentResourceDetectorConfig

[repokitteh-read-only]

Hi @joaopgrassi, welcome and thank you for your contribution.

We will try to review your Pull Request as quickly as possible.

In the meantime, please take a look at the contribution guidelines if you have not done so already.

🐱

Caused by: #29547 was opened by joaopgrassi.

see: more, trace.

[repokitteh-read-only]

CC @envoyproxy/api-shepherds: Your approval is needed for changes made to (api/envoy/|docs/root/api-docs/).
envoyproxy/api-shepherds assignee is @markdroth
CC @envoyproxy/api-watchers: FYI only for changes made to (api/envoy/|docs/root/api-docs/).

🐱

Caused by: #29547 was opened by joaopgrassi.

see: more, trace.

[adisuissa]

Thank you for your contribution.
Here's a first-pass review.
FWIW, it is better to create s series of smaller PRs to increase review speed.

[joaopgrassi]

@adisuissa I fixed the docs CI issues. Now the new proto is present in the API docs.

Here are the changed/new pages:

• Http Tracers includes "OpenTelemetry Resource Detectors" at the bottom
• Resource detectors Will list all resource detectors automatically
• Env resource detector docs for the env resource detector

Sorry for the size of the PR. I wasn't sure if I should break it only adding the detectors and later using. I will keep it in mind for the next ones :)

[phlax]

/docs

for ref @joaopgrassi you can get it to link the docs that it has built in ci - this gives a generic pr link which resolves to commit - you can link these for specific pages

[repokitteh-read-only]

Docs for this Pull Request will be rendered here:

https://storage.googleapis.com/envoy-pr/29547/docs/index.html

The docs are (re-)rendered each time the CI envoy-presubmit (precheck docs) job completes.

🐱

Caused by: a #29547 (comment) was created by @phlax.

see: more, trace.

[RyanTheOptimist]

Looks like a formatting issue?

./source/extensions/tracers/opentelemetry/resource_detectors/resource_detector.h:16: * @brief A strig key-value map that stores the resource attributes.
^
Checked 4800 file(s) and 132399 comment(s), found 1 error(s).
ERROR: spell check failed. Run 'tools/spelling/check_spelling_pedantic.py fix and/or add new words to tools/spelling/spelling_dictionary.txt'

[joaopgrassi]

@RyanTheOptimist sorry, it was a typo. fixed!

[RyanTheOptimist]

Looks like this needs a main merge
/wait

[joaopgrassi]

@RyanTheOptimist updated and solved the conflict. I gave write permission to maintainers on the branch/PR, in case it happens again. Should be good to go!

[joaopgrassi]

/retest