documentation: json-processing

[nimo23]

Description
Actually, json processing is only documented as a part of Json-Rest-Processing (https://quarkus.io/guides/rest-json). I think, json processing deserves an extra category "json processing" in the documentation.

• the documentation does not explain that users can only include either quarkus-jackson or quarkus-jsonb, not both.
• performance considerations about the json-provider. For example, in constrast to json-b, jackson makes heavy use of reflection under the hood for their supported annotations. So I guess, jackson json processing is slower in quarkus than json-b. Not only, because quarkus recommends to avoid reflections.

Would be nice to include a summary of the restrictions and stumbling blocks between those two json processing libraries when using within quarkus.

[nimo23]

There is no such limitation #5969 (comment). So I close this issue.