Support google.type.Decimal in gRPC JSON transcoding

[alrz]

Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe the problem.

Technically this type is not a wrapper type and it's not implemented as a well-known type either yet, but I believe it's perfectly fine to cover it in the deserializer for the time being and accept "123", 123 in addition to the existing { "value", "123" } schema.

Describe the solution you'd like

Accept "123", 123 in addition to the existing { "value", "123" } schema. This may need some options to prevent change in behavior esp. when serializing.

Alternatives

Another way to do this is to let users write their own json converters, but this API is not public right now. (#46712)

[alrz]

tagging @JamesNK, I'm interested to do this if this is something you'd consider for gRPC transcoding support. There's only a few open questions that I'd like to to be addressed beforehand. Thanks.

[alrz]

Closing in favor of #46712, custom converters would be a superset of this request.