[backend] Make the admin property filterable

[Dimfacion]

Proposed changes

• Make the admin property filterable

Related issues

• issue Be able to filter users on admin property #1132

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 26.84%. Comparing base (733e23e) to head (481846b).
Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1133      +/-   ##
============================================
+ Coverage     26.55%   26.84%   +0.28%     
- Complexity     1058     1062       +4     
============================================
  Files           471      471              
  Lines         11192    11192              
  Branches        567      567              
============================================
+ Hits           2972     3004      +32     
+ Misses         8136     8104      -32     
  Partials         84       84              

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