additional comments in .proto and/or build.rs for codegen?

[Deep-co-de]

With an additional comment above the message, you could use it to pass a type-attribute to prost. I could have a look at how to do that, if that would be interesting. The documentation is here. But I'm not sure if type-attributes are right or message-attributes are better. That might solve this question #401, or is that already possible?
We would then only have to clarify what these comments should look like. Maybe you can keep them so general that field-attributes can also be added in a later step.

I'm not sure if these options are available as commandline-args, but I thought that would be possible, otherwise you could definitely outsource the codegen for Rust with a build.rs-script and prost maybe.

[temeddix]

This ongoing PR will enable writing custom attributes:

• feat: Support for marking "RUST-ATTRIBUTE" (type attribute) #405