Description
The main reason for this PR is to align FormRequest with the existing Validation API by using getValidated() and getValidatedInput() methods. It also removes the Individual field access, which is still available through getValidatedInput()->get() and getValidatedInput()->has().

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide