HDDS-10481. Use proto 3 in SCMRatisProtocol.proto

[Russole]

What changes were proposed in this pull request?

• Add REQUEST_TYPE_UNSPECIFIED = 0 to align with proto3 enum default value semantics.
• Migrate SCMRatisProtocol.proto from proto2 to proto3 by replacing required fields with optional.
• Reserve field numbers and names to prevent accidental reuse in future schema changes.
• Add required-equivalent presence checks during deserialization, since proto3 no longer validates required fields when deserialization.
• Add unit tests to verify deserialization fails when required fields are missing

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-10481

How was this patch tested?

• All CI checks passed.
  • https://github.com/Russole/ozone/actions/runs/21537543811
• All added unit tests pass.

[szetszwo]

@Russole , thanks for working on this!

I suggest to move the old proto to test and rename the outer classname to something like Proto2SCMRatisProtocolForTesting. Then, we can create objects, serialize them using Proto2SCMRatisProtocolForTesting (proto2) and deserialize them using SCMRatisProtocol (proto3) for testing compatibility.

[Russole]

Thanks @szetszwo for the review. I’ve updated the patch based on the feedback by adding proto2–proto3 compatibility tests and moving the legacy proto to test scope.

[szetszwo]

@Russole , Thanks for the update! The change looks good. Just have a comment about the file name of the test proto.

[szetszwo]

Please also change the file name to Proto2SCMRatisProtocolForTesting.proto.

[szetszwo]

+1 the change looks good.

[szetszwo]

@Russole , thanks a again for working on this! After merging this PR, filed two related JIRAs HDDS-14561 HDDS-14562; see if you are interested in also working on them.

[Russole]

@szetszwo Appreciate the review and for merging this.
I’m happy to pick up both HDDS-14561 and HDDS-14562.