Added support for modifying the duplicate instance before it's saved

[jackton1]

Closes: #469

[pep8speaks]

Hello @jackton1! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2021-09-06 18:34:39 UTC

[codecov]

Codecov Report

Merging #481 (4fc50ba) into main (e153afb) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main      #481   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines          283       286    +3     
=========================================
+ Hits           283       286    +3     

Impacted Files	Coverage Δ
model_clone/mixins/clone.py	100.00% <100.00%> (ø)

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