Return userid from check_permission

[Maillol]

What do these changes do?

check_permission now returns the userid instead of None.
This avoids an extra authorization lookup for callers.

Are there changes in behavior for the user?

These changes does not break existing logic (only adds a returned value)

Related issue number

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.19%. Comparing base (3ad4302) to head (a7b650d).
⚠️ Report is 237 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #948      +/-   ##
==========================================
+ Coverage   94.13%   94.19%   +0.05%     
==========================================
  Files          11       11              
  Lines         597      620      +23     
  Branches       30       22       -8     
==========================================
+ Hits          562      584      +22     
- Misses         26       27       +1     
  Partials        9        9              

Flag	Coverage Δ
unit	94.19% <100.00%> (+0.05%)	⬆️

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