reworked users.get_details

[bigcat88]

Changes proposed in this pull request:

• users.get_details renamed to get_user and returns a class instead of a dictionary.
• Optional argument displayname in users.create renamed to display_name.

Fixed:

• users.get_details with empty parameter in some cases was raised exception.

[codecov]

Codecov Report

Merging #145 (b772e22) into main (3c189b6) will increase coverage by 0.00%.
The diff coverage is 100.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #145   +/-   ##
=======================================
  Coverage   99.76%   99.77%           
=======================================
  Files          34       34           
  Lines        2976     3059   +83     
=======================================
+ Hits         2969     3052   +83     
  Misses          7        7           

Files	Coverage Δ
nc_py_api/_version.py	100.00% <100.00%> (ø)
nc_py_api/users.py	100.00% <100.00%> (ø)