gRPC Exporter Endpoint Configuration Variable Update

[natemollica-nm]

Changes proposed in this PR

Update consul-telemetry-collector to include gRPC endpoint configuration via environment variable to support Datadog OTLP metrics collection gRPC receiver endpoint.

• Added similar environment variable configuration option to that CO_OTEL_HTTP_ENDPOINT for gRPC receivers: CO_OTEL_GRPC_ENDPOINT
• Added similar CLI parameter flag to that of http-collector-endpoint for gRPC receivers: grpc-collector-endpoint

How I've tested this PR

• Updated external_test.go with grpc forwarding tests

	t.Run("with tls grpc forwarder", func(t *testing.T) {
		provider := NewProvider(&config.ExporterConfig{
			ID: exporters.GRPCOtlpExporterID,
			Exporter: &exporters.ExporterConfig{
				Endpoint: "https://localhost:6060",
			},
		}, providers.SharedParams{})
		retrieved, err := provider.Retrieve(context.Background(), "", nil)
		test.NoError(t, err)

		conf, err := retrieved.AsConf()
		test.NoError(t, err)
		confMap := conf.ToStringMap()
		exporters := asMap(t, confMap["exporters"])
		otlp := asMap(t, exporters["otlp"])
		test.Eq(t, otlp["endpoint"], "https://localhost:6060")
		test.Eq(t, otlp["tls"], nil)
	})

	t.Run("with non-tls grpc forwarder", func(t *testing.T) {
		provider := NewProvider(&config.ExporterConfig{
			ID: exporters.GRPCOtlpExporterID,
			Exporter: &exporters.ExporterConfig{
				Endpoint: "http://localhost:6060",
			},
		}, providers.SharedParams{})
		retrieved, err := provider.Retrieve(context.Background(), "", nil)
		test.NoError(t, err)

		conf, err := retrieved.AsConf()
		test.NoError(t, err)
		confMap := conf.ToStringMap()
		exporters := asMap(t, confMap["exporters"])
		otlp := asMap(t, exporters["otlp"])
		test.Eq(t, otlp["endpoint"], "http://localhost:6060")
		tlsSetting := asMap(t, otlp["tls"])
		test.Eq(t, tlsSetting["insecure"], true)
		test.Eq(t, tlsSetting["insecure_skip_verify"], false)
	})

• Ran make target for go tests.

How I expect reviewers to test this PR

• Review repository updates to include gRPC endpoint environment variable and verify no conflicts with HCP cloud functionality.

Checklist

• Tests added
• [CHANGELOG entry added]