feat!: Raise error on nullable primary key

[AndreasAlbertQC]

Motivation

Implements #160

Changes

• Removed warning for nullable primary keys
• Changed behavior such that attempts to declare nullable primary key columns raise a hard errror

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (ab5224b) to head (2f08d5e).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #173   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           50        50           
  Lines         2901      2897    -4     
=========================================
- Hits          2901      2897    -4     

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