Validate rule guidance strictly.

[blkt]

Summary

This change uses bluemonday library to perform strict validation of guidance field of rule types. In case sanitized input is different from the input itself, rule type creation/update is rejected returning a meaningful error message.

The way input is sanitized is in line with the way it is rendered in the CLI by the glamour library.

Change Type

Mark the type of change your PR introduces:

• Bug fix (resolves an issue without affecting existing features)
• Feature (adds new functionality without breaking changes)
• Breaking change (may impact existing functionalities or require documentation updates)
• Documentation (updates or additions to documentation)
• Refactoring or test improvements (no bug fixes or new functionality)

Testing

Manual tests.

Review Checklist:

• Reviewed my own code for quality and clarity.
• Added comments to complex or tricky code sections.
• Updated any affected documentation.
• Included tests that validate the fix or feature.
• Checked that related changes are merged.

[blkt]

Note: this might be overly strict in that characters like ' are mapped to ', which is otherwise acceptable. An alternative might be to use a custom policy to strip just HTML tags.

I'll put this back to draft and verify what options we have.

[JAORMX]

Good idea

[JAORMX]

this validation probably merits adding unit tests

[coveralls]

coverage: 53.936% (+0.3%) from 53.663%
when pulling afcff20 on issue-4286-strict
into a8b4f81 on main.

[JAORMX]

Love the focus on input validation. Thanks for doing this!