auth: Convert check() and related blocking fns to async

[eth3lbert]

This PR focuses on converting the check() and related implementations to async, so there might be spawn_blocking() fns in controllers that can be removed. However, I expect these changes to be made in a separate PR :)

[codecov]

Codecov Report

Attention: Patch coverage is 97.63780% with 3 lines in your changes missing coverage. Please review.

Project coverage is 88.88%. Comparing base (e35a4f5) to head (5fcdaf4).
Report is 17 commits behind head on main.

Files with missing lines	Patch %	Lines
src/controllers/user/update.rs	50.00%	2 Missing ⚠️
src/auth.rs	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9872      +/-   ##
==========================================
+ Coverage   88.85%   88.88%   +0.02%     
==========================================
  Files         289      289              
  Lines       30002    30080      +78     
==========================================
+ Hits        26659    26737      +78     
  Misses       3343     3343              

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[Turbo87]

nice work! 👍