[Feature Request] Use JSONC for body

**Is your feature request related to a problem? Please describe.**
There are a lot of cases where being able to comment out parts of the JSON body would be useful. e.g. Quickly switching between different body content, alternating between different JWTs (env vars). It would also be useful for leaving comments for future reference.

**Describe the solution you'd like**
To use JSONC in place of or in addition to JSON for the body type. This would allow comments in the JSON that would be ignored by the parser.

**Describe alternatives you've considered**
The only alternative is to store alternate body content elsewhere (e.g. external doc) or, in the case of env vars, rename "commented out" var to something not in use.

The issue names no files, tests, or entry points. Search the repository for JSON body handling and the parser dependency, then verify that body content accepts JSONC comments while ordinary JSON behavior remains intact.

Written by the indexing model from the issue text.