feat: add soft delete mixin

[Kumzy]

Creating a mixin for soft delete.

Do you think we need more in the Mixin?

Missing tests + repository changes + documentation

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.32%. Comparing base (c5ea0c9) to head (868b1bb).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
advanced_alchemy/mixins/softdelete.py	0.00%	14 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #337      +/-   ##
==========================================
- Coverage   82.43%   82.32%   -0.11%     
==========================================
  Files         105      106       +1     
  Lines        9039     9053      +14     
  Branches     1219     1219              
==========================================
+ Hits         7451     7453       +2     
- Misses       1262     1274      +12     
  Partials      326      326              

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[hasansezertasan]

I love the idea, soft deletes rules!

That said, I'd love AA to have deeper support for it. Such as deletion-aware repository/service methods like get_one, list, etc.