add generic return value for .filter and .sort

[bobbyrenwick]

This preserves the typing information when calling filter.sort and filter.filter on the SQLAlchemy Filters.

This works with pylance but seems like it's failing with mypy on CI.

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[codecov]

Codecov Report

Merging #489 (8c75b58) into main (95ae1ad) will not change coverage.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #489   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines          193       195    +2     
=========================================
+ Hits           193       195    +2     

Files	Coverage Δ
fastapi_filter/contrib/sqlalchemy/filter.py	100.00% <100.00%> (ø)

[DamianHeardJudo]

I am curious if the maintainer have have any appetite to get an updated version of this PR merged? As it stands the type hints provide aren't overly useful with mypy.

[arthurio]

I like when things work properly, so yes, if we get something that works with both pylance and mypy I would be very happy to merge and ship it! Does it help that support for python 3.8 has dropped?