Support extensions for tags

[kkolur]

🚀 Feature

Tags have been implemented at the root level as a result of this PR. According to OpenAPI extensions should be available to the Tag object as well.

For example, ReDoc has some vendor extensions available for Tag Objects. You can see here how its used and how its rendered

[johanbrandhorst]

Thanks for the feature request! I think we need to take a holistic view at extensions, the page you linked details all the places where extensions can exist in the OpenAPIv2 spec. It would make sense to me to add a message to describe the extension type and then add that to all the places extensions can be specified. What do you think?

[kkolur]

Thanks for the feature request! I think we need to take a holistic view at extensions, the page you linked details all the places where extensions can exist in the OpenAPIv2 spec. It would make sense to me to add a message to describe the extension type and then add that to all the places extensions can be specified. What do you think?

@johanbrandhorst sorry im having trouble understanding the following, can you provide an example?

It would make sense to me to add a message to describe the extension type and then add that to all the places extensions can be specified

Do you mean we should create seperate Messages for every place extensions can be added to? Like SwaggerExtensions, OperationExtensions, InfoExtensions, TagExtensions, etc?

For most places already in protoc-gen-openapiv2, extensions are added to the messages (Swagger, Operation, Info, etc) like so: Example here

I was thinking we just follow the same pattern by adding the following line of code to the Tag Message:

map<string, google.protobuf.Value> extensions = 3;

And then do the necessary Go changes

Thoughts?

[johanbrandhorst]

You're right, I didn't think we already had extensions in some places, so lets just go ahead and continue that pattern.

[johanbrandhorst]

Fixed in #2950