feat(cat-gateway): Updated Catalyst Signed Document validation

[Mr-Leshiy]

Description

Modifying Catalyst Signed Documents validation rules, by applying updated crate version cardano-foundation/catalyst-libs#574.
New rules enforces to always have a parameters (category_id) metadata field for all document types (Proposal, Comment, Proposal Submission Action), and it's no longer optional.
Any Proposal, Comment or Proposal Submission Action which would be referencing any fund 14 template would be rejected.

Added fund 15 hardcoded document ids, with the fund 14 content (will be updated later).

Please confirm the following checks

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream module

[stanislav-tkach]

I was curious and checked that: as far as I can see, the rustfmt::skip does nothing here. Perhaps it was useful before we made some of the formatting changes, but unless I'm missing something it can be removed now.