feat(bookings): forward custom question answers to success redirect

[OmkarKovvali]

What does this PR do?

This PR updates the booking success redirect logic to include custom question responses in the URL parameters. It adds support for multi-select answers to be forwarded as multiple URL parameters. Example is ?option=A&option=B instead of a single comma-separated string, while maintaining backward compatibility for existing array fields like hostname.

Before this PR, when "forward parameters" was enabled, only standard fields such as name email and date were included. Custom questions were ignored. Additionally, multi-select answers were flattened into a single string, making them hard to parse by external tooling.

• Fixes Ability for custom question field parameter forwarding for booking success redirect URL #25192 (GitHub issue number)

Visual Demo (For contributors especially)

Mandatory Tasks (DO NOT REMOVE)

• [X ] I have self-reviewed the code (A decent size PR without self-review might be rejected).
• [X ] I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. If N/A, write N/A here and check the checkbox.
• [ X] I confirm automated tests are in place that prove my fix is effective or that my feature works.

How should this be tested?

1. Standard Booking Redirect: Book a regular meeting with no custom fields and verify the redirect url contains standard params like hostName and date like before.

2. Custom text question: create an event type with a custom question like "Company Name" and book it and answer "Acme". Verify the redirect url contains &company_name=Acme.

3. Multi-select custom question: Create an event type with Checkboxes question e.g. "Dietary Requirements" and book it, selecting "Vegan" AND "Gluten-free". Verify the redirect URL contains &dietary=Vegan&dietary=Gluten%20Free. Verify that its not just &dietary=Vegan,Gluten Free.

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[OmkarKovvali]

@dhairyashiil @keithwillcode @CarinaWolli Please lmk if there's anything else to add :)

[OmkarKovvali]

Hi Team, looking for feedback to merge this PR. Please lmk what the next steps are.