refactor: create deploy candidate apps

[18alantom]

fix issue that causes DC to not update apps source even if RG app source has changed

occurs if theres a previous deploy with an old app source

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 79.76190% with 17 lines in your changes missing coverage. Please review.

Project coverage is 43.18%. Comparing base (72adf59) to head (3f25f8c). Report is 2050 commits behind head on master.

Files	Patch %	Lines
press/press/doctype/app_source/app_source.py	9.09%	10 Missing :warning:
press/press/doctype/release_group/release_group.py	90.41%	7 Missing :warning:

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #1573       +/-   ##
===========================================
+ Coverage   31.74%   43.18%   +11.44%     
===========================================
  Files         316      317        +1     
  Lines       22061    22112       +51     
===========================================
+ Hits         7003     9549     +2546     
+ Misses      15058    12563     -2495     

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[18alantom]

I don't think I'm gonna get back to this.