Missing sqlalchemy operators

[JakNowy]

This implements #79 by introducing FastCRUD._get_sqlalchemy_filter() method and a dictonary of filter mappings in FastCRUD._SUPPORTED_FILTERS. Adding new sqlalchemy opertors is as simple as extending the dictonary.

It also solves the or_() operator issue:

                    ItemCRUD.get_multi(
                        name__or={'startswith': 'foo', 'endswith': 'bar'}
                    )

There is some mypy issue which I struggle to solve, but it looks like it's not required. The tests pass with good coverage.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (03d4a2d) to head (c53f7f0).
Report is 16 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##              main       #85    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files           68        70     +2     
  Lines         4819      5415   +596     
==========================================
+ Hits          4819      5415   +596     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[JakNowy]

@igorbenav this is ready for review. I'm going to add some docs tomorrow.