Add user management

[pohlm01]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 95.18950% with 33 lines in your changes missing coverage. Please review.

Project coverage is 74.17%. Comparing base (fa61cae) to head (d6b0105).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
openadr-vtn/src/error.rs	40.42%	28 Missing ⚠️
openadr-vtn/src/data_source/postgres/user.rs	99.41%	2 Missing ⚠️
openadr-vtn/src/api/user.rs	99.60%	1 Missing ⚠️
openadr-vtn/src/main.rs	0.00%	1 Missing ⚠️
openadr-wire/src/lib.rs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #126      +/-   ##
==========================================
+ Coverage   70.41%   74.17%   +3.76%     
==========================================
  Files          39       40       +1     
  Lines        4841     5457     +616     
==========================================
+ Hits         3409     4048     +639     
+ Misses       1432     1409      -23     

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