Add support for multiple approval rules

[gdubicki]

Support for #388 and #95.

[codecov-commenter]

Codecov Report

Merging #435 (61beba2) into main (278f535) will increase coverage by 0.22%.
The diff coverage is 94.44%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #435      +/-   ##
==========================================
+ Coverage   86.93%   87.15%   +0.22%     
==========================================
  Files          65       67       +2     
  Lines        2258     2313      +55     
==========================================
+ Hits         1963     2016      +53     
- Misses        295      297       +2     

Impacted Files	Coverage Δ
gitlabform/gitlab/projects.py	68.04% <ø> (-6.58%)	⬇️
...tlabform/processors/multiple_entities_processor.py	96.20% <ø> (-0.19%)	⬇️
gitlabform/processors/defining_keys.py	72.05% <80.00%> (ø)
...labform/gitlab/project_merge_requests_approvals.py	87.50% <87.50%> (ø)
gitlabform/configuration/transform.py	95.33% <98.57%> (+2.31%)	⬆️
gitlabform/constants.py	100.00% <100.00%> (ø)
gitlabform/gitlab/__init__.py	100.00% <100.00%> (ø)
gitlabform/gitlab/branches.py	87.71% <100.00%> (-1.00%)	⬇️
gitlabform/gitlab/core.py	94.81% <100.00%> (+0.15%)	⬆️
gitlabform/processors/abstract_processor.py	89.23% <100.00%> (+0.52%)	⬆️
... and 3 more