[IMPROVE] Allow webhook message to respond in thread

[Karting06]

Proposed changes

At the moment, outgoing integrations can only respond in the form of a message (and not as an answer in a thread).
With this change, if a tmid is received, it will respond as an answer to a thread instead of a message.

Issue(s)

How to test or reproduce

Screenshots

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• Improvement (non-breaking change which improves a current function)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Hotfix (a major bugfix that has to be merged asap)
• Documentation Update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works (if applicable)
• I have added necessary documentation (if applicable)
• Any dependent changes have been merged and published in downstream modules

Changelog

Adds ability to outgoing integration to respond in a thread.

Further comments

I don't know if tests are needed, and don't really know how to make them.