Add ReceiveSendGreetingServlet and publish workflow for matrix project

[samarth-gupta-traceable]

Description

Add ReceiveSendGreetingServlet.java and publish workflow for matrix project

1. new servelt ReceiveSendGreetingServlet is capable of handling POST request data and echo is back
2. new git workflow for publishing the docker images for various servlet containers is triggered only when changes are made to matrix project path and main branch.

Testing

Please describe the tests that you ran to verify your changes. Please summarize what did you test and what needs to be tested e.g. deployed and tested helm chart locally.

Checklist:

• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been merged and published in downstream modules

Documentation

Make sure that you have documented corresponding changes in this repository or hypertrace docs repo if required.

[pavolloffay]

Some files have OTEL license header and some not, could we add the license header to the missing files? We should preserve OTEL license header.

[samarth-gupta-traceable]

Some files have OTEL license header and some not, could we add the license header to the missing files? We should preserve OTEL license header.

@pavolloffay Below files do not have OTEL header (with reason for missing):

1. ExceptionRequestListener.java: Source file in OTEL repo itself does not have the header. I can add it though if desirable. https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/smoke-tests/matrix/src/main/java/io/opentelemetry/smoketest/matrix/ExceptionRequestListener.java
2. GreetingWithHeader , StreamTransferUtil, ReceiveSendGreetingServlet : does not exists in OTEL repo and are added by us for HT. If needed I can add header in these as well.

[pavolloffay]

https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/smoke-tests/matrix/src/main/java/io/opentelemetry/smoketest/matrix/ExceptionRequestListener.java

please add it to our copy. Also in the matrix readme mention that this is from OTEL

[samarth-gupta-traceable]

https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/smoke-tests/matrix/src/main/java/io/opentelemetry/smoketest/matrix/ExceptionRequestListener.java

please add it to our copy. Also in the matrix readme mention that this is from OTEL

done 👍

[pavolloffay]

Could we rename it EchoServlet?

[pavolloffay]

Could do servlet just simply read the body to a buffer and write it back with the same content type?

This way we don't need dep on Gson and additional classes. To test response heders capture the servlet could also send some test response header.

[samarth-gupta-traceable]

@pavolloffay made below changes.

1. renamed the servlet to EchoServlet
2. copying request as response . Header going as test headers.