Add and populate user on cronjobs and creator on triggers (SYN-8229, SYN-6850)

[Cisphyx]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 98.80952% with 1 line in your changes missing coverage. Please review.

Project coverage is 96.40%. Comparing base (41ed219) to head (7c72475).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
synapse/lib/agenda.py	93.75%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4043      +/-   ##
==========================================
- Coverage   96.48%   96.40%   -0.08%     
==========================================
  Files         256      256              
  Lines       59685    59749      +64     
==========================================
+ Hits        57585    57604      +19     
- Misses       2100     2145      +45     

Flag	Coverage Δ
linux	96.40% <98.80%> (-0.01%)	⬇️
linux_replay	?

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[vEpiphyte]

We should discuss this; since previously we've talked about maintaining (or adding where it is missing) the creator field onto structures as an immutable value, and then having a user value that would represent who the associated query would execute as.

[MichaelSquires]

There's a small nit about whitespace in the tests but looks good otherwise.

[invisig0th]

Do we need to stage an Optic release to account for these changes (with a minver on the Optic side) to avoid compat issues?

[invisig0th]

placing a hold on this for corresponding Optic updates

Discussed and accounted for