fix: remove traditional validation rule param types (1/2)

[kenjis]

Description
Fixes #6489

To add declare(strict_types=1). See #8072
There is no guarantee that a string will be passed, so declaring strict types may result in a TypeError.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[MGatner]

If the intent is to support anything that would have been juggled to a string then shouldn't our @param tags be scalar|null instead? And maybe also Stringable?

[kenjis]

I don't see much point in thinking too much about @param.

The traditional validation rules assumed strings. They were originally designed to validate POST data, so the values are all strings. null is for when the key of the array data to validate is missing.

I don't want the traditional rules to be used and would like to remove them, but I am not sure if apps migrated from older CIs will not have any problems when switching to the strict rules..

[kenjis]

Added docs.

[MGatner]

Fair enough. This is basically a "pre-deprecation" change required so we can enact strict types.