Add cascade deletion for application_user_roles

[keigohtr]

What is this PR for?

Because of the ForeignKey, we cannot delete Application model when we use an authentication.

This PR includes

• Add backref to delete orphan
• Change the way of deletion since query().delete() doesn't support cascade deletion (See link)

What type of PR is it?

Bugfix

What is the issue?

N/A

How should this be tested?

python -m unittest drucker_dashboard/test/test_access_control.py

[codecov-io]

Codecov Report

Merging #56 into master will increase coverage by 0.13%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #56      +/-   ##
==========================================
+ Coverage   79.12%   79.26%   +0.13%     
==========================================
  Files          36       36              
  Lines        1586     1596      +10     
==========================================
+ Hits         1255     1265      +10     
  Misses        331      331

Impacted Files	Coverage Δ
drucker_dashboard/apis/api_evaluation.py	57.27% <ø> (-0.39%)	⬇️
drucker_dashboard/models/evaluation_result.py	81.48% <100%> (+2.31%)	⬆️
drucker_dashboard/models/application_user_role.py	100% <100%> (ø)	⬆️
drucker_dashboard/models/evaluation.py	93.75% <100%> (+0.41%)	⬆️
drucker_dashboard/utils/__init__.py	78.72% <100%> (+3.11%)	⬆️
drucker_dashboard/apis/api_kubernetes.py	86.69% <100%> (ø)	⬆️

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[yoquankara]

If you are using backref and setting ondelete='CASCADE, I think bulk delete is possible by adding passive_deletes=True to backref.
By doing so, there is no need to modify drucker_dashboard/apis/api_kubernetes.py?

Ref: https://docs.sqlalchemy.org/en/latest/orm/collections.html#using-passive-deletes

[keigohtr]

@yoquankara Thank you for reviewing this!
I have updated to use passive_delete -> 5b4950b

[keigohtr]

@yuki-mt I have changed evaluation related models. I confirmed it passes test but could you check it please? -> 1fedc08

[yuki-mt]

@keigohtr Looks good! Could you also delete the line https://github.com/rekcurd/drucker-dashboard/blob/master/drucker_dashboard/apis/api_evaluation.py#L87-L88 ?
It is not necessary when ondelete='CASCADE' works.

[keigohtr]

@yuki-mt Thank you for reviewing it!
I have removed unnecessary line you mentioned. -> 9b0079f

[yuki-mt]

LGTM!