fix: no validation error when accepted formats not entered (resolves #1830)

[jobara]

Resolves #1830

• Fixes validation requirements for accepted formats
• Expand test coverage for engagement related validation errors
• Refactor tests to make use of pest's helper functions

Prerequisites

If this PR changes PHP code or dependencies:

• [x] I've run composer format and fixed any code formatting issues.
• [x] I've run composer analyze and addressed any static analysis issues.
• [x] I've run php artisan test and ensured that all tests pass.
• [x] I've run composer localize to update localization source files and committed any changes.

If this PR changes CSS or JavaScript code or dependencies:

• [ ] I've run npm run lint and fixed any linting issues.
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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (0458cf9) 97.65% compared to head (a24ee92) 97.65%. Report is 1 commits behind head on dev.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #2107 +/- ## ========================================= Coverage 97.65% 97.65% Complexity 2103 2103 ========================================= Files 313 313 Lines 9535 9543 +8 ========================================= + Hits 9311 9319 +8 Misses 224 224 ```

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