This issue has been migrated from [#16365](https://github.com/matrix-org/synapse/pull/16365). --- <!-- Fixes: # <!-- --> <!-- Supersedes: # <!-- --> <!-- Follows: # <!-- --> <!-- Part of: # <!-- --> Base: `develop` <!-- git-stack-base-branch:develop --> <!-- This pull request is commit-by-commit review friendly. <!-- --> <!-- This pull request is intended for commit-by-commit review. <!-- --> Original commit schedule, with full messages: <ol> <li> Add warnings when /forget isn't given a JSON body </li> </ol>
