chore: Refactor FTLR IsUnique case

Squashed commit of the following:

commit d0321c1
Author: June Rousseau <[email protected]>
Date:   Sun Sep 15 15:16:19 2024 +0200

    chore: remove deadname

commit 081649d
Author: June Rousseau <[email protected]>
Date:   Sun Sep 15 15:15:19 2024 +0200

    chore: Prettify and cleaning proof isunique FTLR

commit d31966c
Author: June Rousseau <[email protected]>
Date:   Sun Sep 15 01:14:46 2024 +0200

    Refactor FTRL IsUnique done (but still a bit ugly)

commit 5e46e40
Author: June Rousseau <[email protected]>
Date:   Sat Sep 14 18:42:13 2024 +0200

    WIP refactor FTRL, proof QED, still need some refactoring

commit a605122
Author: June Rousseau <[email protected]>
Date:   Fri Sep 13 17:37:46 2024 +0200

    WIP refactor ftlr is_unique