Add support for MS Teams webhooks

[dangrier]

Implements #5964 to add Microsoft Teams webhooks (Incoming Webhook Connector).

Largely matched styling of Discord webhooks and aligned with other webhook functionality/appearance.

Tested on a local instance, with a connection to Teams and functioned as expected.

All commits signed off, and latest changes integrated from upstream.

[codecov-io]

Codecov Report

Merging #6632 into master will decrease coverage by 0.48%.
The diff coverage is 0.73%.

@@            Coverage Diff             @@
##           master    #6632      +/-   ##
==========================================
- Coverage   41.35%   40.87%   -0.49%     
==========================================
  Files         415      416       +1     
  Lines       56337    57013     +676     
==========================================
+ Hits        23299    23303       +4     
- Misses      29917    30589     +672     
  Partials     3121     3121

Impacted Files	Coverage Δ
models/webhook_msteams.go	0% <0%> (ø)
models/webhook.go	60.16% <0%> (-0.91%)	⬇️
modules/auth/repo_form.go	41.73% <0%> (-0.74%)	⬇️
routers/repo/webhook.go	1.39% <0%> (-0.13%)	⬇️
modules/setting/webhook.go	100% <100%> (ø)	⬆️
routers/routes/routes.go	82.18% <100%> (+0.09%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2af67f6...98d4786. Read the comment docs.

[dangrier]

Is there anything else needed for approval?

[techknowlogick]

@dangrier could you resolve git conflicts, and post screenshots of what a webhook would look like in MS Teams?

[techknowlogick]

@dangrier I've just resolved the git conflicts. I did it via Github interface so hopefully a make fmt isn't needed.

[dangrier]

Okay, didn't see that so also resolved - but not to worry!

It looks like this:

[techknowlogick]

@dangrier ah phew. glad that was quick to diagnose.