Error when mesh gateway mode not set

[lkysow]

To prevent users from being confused as to why their traffic isn't being
routed, give an error on connect injection if they've configured an
upstream to use a datacenter but they don't have a proxy-defaults config
with mesh gateway mode set to local or remote.

NOTE: No ACL changes need to be made because proxy-defaults does not require an ACL for reads (https://www.consul.io/api-docs/config#get-configuration)

How I tested:

• Install with:

  global:
    name: consul
    imageK8S: ghcr.io/lkysow/consul-k8s-dev:jan20
    acls:
      manageSystemACLs: true
  connectInject:
    enabled: true
  controller:
    enabled: true
  server:
    replicas: 1

• Apply

  apiVersion: v1
  kind: ServiceAccount
  metadata:
    name: static-client
  ---
  apiVersion: v1
  kind: Pod
  metadata:
    name: luke
    annotations:
      "consul.hashicorp.com/connect-inject": "true"
      "consul.hashicorp.com/connect-service-upstreams": "static-server:1234:dc2"
  spec:
    containers:
      - name: static-client
        image: tutum/curl:latest
        command: [ "/bin/sh", "-c", "--" ]
        args: [ "while true; do sleep 30; done;" ]
        ports:
          - containerPort: 8080
            name: http
    serviceAccountName: static-client

• Errors with

  Error from server: error when creating "scratch/static-client.yaml": admission webhook "consul-connect-injector.consul.hashicorp.com" denied the request: Error configuring injection init container: upstream "static-server:1234:dc2" is invalid: there is no ProxyDefaults config to set mesh gateway mode
  

• Apply

  apiVersion: consul.hashicorp.com/v1alpha1
  kind: ProxyDefaults
  metadata:
    name: global
  spec:
    meshGateway:
      mode: local

• Re-apply static-client, it will schedule

Checklist:

• Tests added
• CHANGELOG entry added (HashiCorp engineers only, community PRs should not add a changelog entry)

[thisisnotashwin]

EXCELLENT!

[kschoche]

This is a super nice fix to have, great work!