feat(relay): Add endpoint for registering trusted relay

[iambriccardo]

This PR exposes a new endpoint for registering an external Relay to Sentry.

This endpoint can be authenticated exclusively with the organization auth token, since it's meant to be used in a cli environment.

Closes: https://github.com/getsentry/team-ingest/issues/275

[codecov]

Codecov Report

Attention: Patch coverage is 95.08197% with 3 lines in your changes missing coverage. Please review.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...y/api/endpoints/internal_register_trusted_relay.py	95.08%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #82808      +/-   ##
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+ Coverage   80.36%   80.46%   +0.10%     
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  Files        7273     7295      +22     
  Lines      321301   321917     +616     
  Branches    20948    20948              
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+ Hits       258224   259045     +821     
+ Misses      62675    62470     -205     
  Partials      402      402