protoc-gen-openapiv2: Use json_name when generating required field names

[patrick246]

References to other Issues or PRs

Fixes #2874

Have you read the Contributing Guidelines?

yes

Brief description of what is fixed or changed

Fix the bug from #2874 where the required fields section in the JSON schema would contain autogenerated field names, even when fields had a custom json_name value set. These would then not match up with the actual fields defined in the schema, resulting in an invalid OpenAPI spec.

This adds checks if we need to convert Protobuf field names into JSON field names in template.go schemaOfField and nestedQueryParams and removes a check from updateswaggerObjectFromJSONSchema that assumed no json_name was set and prevented another conversion in renderMessageAsDefinition from working.

The PR also contains additions to the tests for functions that were modified, in addition to examples in a_bit_of_everything.proto.

Other comments

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[patrick246]

I'll have to debug the failing CLA check tomorrow, there should be a signed corporate CLA in place

[johanbrandhorst]

LGTM

[johanbrandhorst]

Looks like we got a formatting diff in the proto changes, you can fix it with buf format.

[johanbrandhorst]

@oyvindwe could you please have a look at this as well?

[johanbrandhorst]

Thanks for your contribution!

[patrick246]

Hi, are there already plans for releasing this?

[johanbrandhorst]

Sure, we have a few in-flight PRs (#2928, #2904) but if we don't move forward on those soon I can cut another minor.