Refactor: prevent DonationFormRepository::prepareQuery() to return forms without the "formBuilderSettings" and "formBuilderFields" meta keys

[glaubersilva]

Description

All forms created using the visual form builder include the formBuilderSettings and formBuilderFields meta keys since the Give 3.0.0 version, and the DonationForm model relies on these meta keys to work properly.

However, the DonationFormRepository::prepareQuery() method was returning posts even when these meta keys were empty which can throw fatal errors.

Even though this is not a common situation as forms are always created with these meta keys, unforeseen events like accidental deletions made directly through DB can happen.

So this PR prevents returning posts without these meta keys focusing more on a defensive approach that can avoid future problems if they happen.

To better context: my logic here is that as we are relying on this meta key in the isV3Form() method to define if a form is V3 or not, I believe the DonationFormRepository::prepareQuery() also should consider it and not return forms without it.

Affects

The DonationFormRepository::prepareQuery() method.

Testing Instructions

In your terminal, run the following commands:

composer test -- --filter TestDonationFormRepository::testShouldNotReturnDonationFormWithoutSettingsMetaKey
composer test -- --filter TestDonationFormRepository::testShouldNotReturnDonationFormWithoutFieldsMetaKey

Pre-review Checklist

• Acceptance criteria satisfied and marked in related issue
• Relevant @unreleased tags included in DocBlocks
• Includes unit tests
• Reviewed by the designer (if follows a design)
• Self Review of code and UX completed

[alaca]

Looks good 👍