- Works the same as insertUnique, but doesn't return a key
- For SQL databases this can be twice as fast since there is no SELECT
  to get the key after the original INSERT
commit 093b2347762e15a12fc4422c718d6adeb3e7fb89
Author: Luke Seale <19484084+lbseale@users.noreply.github.com>
Date:   Tue Jan 24 17:33:41 2023 -0800
    Add a test for insertUnique_
commit 75ffc4f3eb5048d1983fab6d8b0df22e1d6f4517
Author: Luke Seale <19484084+lbseale@users.noreply.github.com>
Date:   Tue Jan 24 17:33:19 2023 -0800
    Add help for insertUnique_
    - Also fix incorrect type annotation
commit bc81b359f454d0984062ab4f32980df75a6a85d8
Author: Luke Seale <19484084+lbseale@users.noreply.github.com>
Date:   Tue Jan 24 17:31:50 2023 -0800
    Add insertUnique_ to PersistUniqueWrite typeclass
    - Works the same way is insertUnique, but calls insert_ instead of
      insert
    - Return type is Maybe (), since it insert_ doesn't return a key