[BUG] Uniqueness only works on lists of primitive values

[mivanovcpd]

Description

Messages in Protobuf have overridden equals method so they can usually be compared correctly.
Suppose we have the following:

message Person {
  optional string name = 1 [(buf.validate.field).required = true];
  optional string family = 2 [(buf.validate.field).required = true];
}
message Persons {
  repeated PersonName persons = 1 [(buf.validate.field).repeated.unique = true];
}

Steps to Reproduce

1. Create the relevant proto file as described above and write a test to validate a message from the generated model.

Expected Behavior

The validation should work.

Actual Behavior

The validation fails because the protovalidate-java doesn't support unique constraint on non-primitive types.

Environment

• Operating System: Linux
• Version: Mint
• Compiler/Toolchain: Kotlin
• Protovalidate Version: 0.1.8

Possible Solution

Disable the restriction in the code and allow arbitrary things to be compared to ensure uniqueness.

[pkwarren]

This is documented in the validate schema and not specific to the Java implementation: https://github.com/bufbuild/protovalidate/blob/7c3e2e3847b75e892b49411c788c350c5e272288/proto/protovalidate/buf/validate/validate.proto#L3316-L3318

There is a similar but not identical issue reported upstream in the protovalidate repo: bufbuild/protovalidate#92. I'd suggest opening a feature request there as any changes would need to be first made there, then verified in conformance tests, and then make their way to all of the language implementations.