Add OTLP trace with ADC example

[damemi]

Cobbled this together following docs from:

• https://opentelemetry.io/docs/languages/java/exporters/
• https://github.com/googleapis/google-auth-library-java
• https://github.com/googleapis/google-auth-library-java/blob/main/samples/snippets/src/main/java/AuthenticateExplicit.java
• https://cloud.google.com/java/docs/reference/google-auth-library/latest/com.google.auth.oauth2.GoogleCredentials
• https://javadoc.io/static/io.opentelemetry/opentelemetry-exporter-otlp-http-trace/1.14.0/io/opentelemetry/exporter/otlp/http/trace/OtlpHttpSpanExporterBuilder.html

Same idea as GoogleCloudPlatform/opentelemetry-operations-go#800, GoogleCloudPlatform/opentelemetry-operations-python#307, and GoogleCloudPlatform/opentelemetry-operations-js#676

[psx95]

Is this different from this example which is already present ?

It seems similar.

[psx95]

Is this different from this example which is already present ?

It seems similar.

Ah, nvm it uses OTLP Span exporter instead of Google Cloud Exporter.

[psx95]

The sample looks good. A couple of follow-ups:

• Should we move it to the existing examples folder ? The proposed example is placed in a folder called example.
• Could we add a corresponding gradle file along with a small Readme with instructions to build and run this example so that it remains consistent with the rest of the examples.

[psx95]

Looks good to me! Thanks @damemi ! 👍🏻

Following from our offline discussion, two pending action items prior to merging -

• Adding -Dotel.exporter.otlp.protocol=http/protobuf' to the autoconf_config in build.gradle
• Adding a README file under examples/otlptrace to give an overview of this example and instructions on running it.

[damemi]

Thanks for all your help @psx95! I added the changes we talked about and tested this and it's working now 🎉