Enhance createapplication command to display autogenerated secret

[n2ygk]

Fixes #1151

Description of the Change

Enhance the createapplication management command to display the cleartext secret when it's been autogenerated since it gets stored hashed. Also display the client name or ID. And improves the --help documentation.

Checklist

• PR only contains one change (considered splitting up PR)
• unit-test added
• documentation updated
• CHANGELOG.md updated (only for user relevant changes)
• author name in AUTHORS

[codecov]

Codecov Report

Merging #1152 (4cd0c61) into master (025cd1b) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1152   +/-   ##
=======================================
  Coverage   96.87%   96.87%           
=======================================
  Files          31       31           
  Lines        1790     1794    +4     
=======================================
+ Hits         1734     1738    +4     
  Misses         56       56           

Impacted Files	Coverage Δ
..._provider/management/commands/createapplication.py	100.00% <100.00%> (ø)

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[rcmurphy]

One typo in the changelog; otherwise looks good!