chore: add equals, hashCode, and toString methods to client interface impls

[vcrfxia]

Description

Context: #5671 (comment)

Testing done

Non-functional change.

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")

[agavra]

Probably a good idea to also add EqualsTester tests for this

[big-andy-coates]

Can you please add unit tests for this new methods?

Otherwise, what tends to happen is people come add new fields and forget to add them to equals and hashcode.

You can test them using the Guava EqualsTester

[vcrfxia]

Added EqualsTester tests, though I'm confused about the statement

Otherwise, what tends to happen is people come add new fields and forget to add them to equals and hashcode.

If someone added a new field, the EqualsTester test wouldn't actually fail, right?. The EqualsTester test is only useful for catching these slip-ups if the person updating the class happens to spot the test in the unit test file and thinks to update the test.