Update logic for adding/editing users

[janash]

This PR updates logic on the page for adding/editing users. The main change made is that the create function is now used for creating a new user, which will result in default roles (user) and groups being set. If a user is not added to a group, a new group is created with their username.

Note that this PR is dependent on molssi-seamm/seamm_datastore#31 in the SEAMM datastore.

[codecov]

Codecov Report

Attention: Patch coverage is 14.28571% with 12 lines in your changes are missing coverage. Please review.

Project coverage is 46.03%. Comparing base (104b355) to head (7003d79).
Report is 9 commits behind head on main.

Files	Patch %	Lines
seamm_dashboard/routes/api/users.py	14.28%	12 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #154      +/-   ##
==========================================
- Coverage   46.62%   46.03%   -0.59%     
==========================================
  Files          35       35              
  Lines        2074     2070       -4     
==========================================
- Hits          967      953      -14     
- Misses       1107     1117      +10     

Flag	Coverage Δ
unittests	46.03% <14.28%> (-0.59%)	⬇️

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[paulsaxe]

LGTM ... but what do I know? At the limits of my understanding.