Code Review Bench PR #25593 - fix(api): return original email without OAuth suffix in bookings

[tomerqodo]

Code Review Bench PR calcom#25593

Original PR Title: fix(api): return original email without OAuth suffix in bookings
Original PR Description: ## What does this PR do?

This PR fixes a bug in API v2 (2024-08-13) where emails in booking API responses contained the OAuth client ID as a suffix (+{cuid}). This suffix exists to prevent email collisions between managed users of different OAuth clients.

Fixes calcom#25494 | Linear: CAL-6843

Problem:

• Managed user emails were returned as: bob+cmidditrv0000mza4q93hbcau@example.com
• Expected display: bob@example.com

Solution:
To avoid breaking changes for platform customers who may rely on the original email format, we preserve the original email field and add a new displayEmail field with the CUID suffix removed.

Key Changes:

• Add getDisplayEmail() helper to strip CUID suffix from emails
• Add displayEmail field to all relevant response objects
• Keep original email field unchanged for backwards compatibility

Regex pattern used: /\+[a-zA-Z0-9]{25}/ (CUID format, consistent with google-calendar.service.ts)

Affected Fields

Field	Value
hosts[].email	bob+{cuid}@example.com (unchanged)
hosts[].displayEmail	bob@example.com (new)
attendees[].email	bob+{cuid}@example.com (unchanged)
attendees[].displayEmail	bob@example.com (new)
bookingFieldsResponses.email	bob+{cuid}@example.com (unchanged)
bookingFieldsResponses.displayEmail	bob@example.com (new)
bookingFieldsResponses.guests[]	guest+{cuid}@example.com (unchanged)
bookingFieldsResponses.displayGuests[]	guest@example.com (new)
reassignedTo.email	bob+{cuid}@example.com (unchanged)
reassignedTo.displayEmail	bob@example.com (new)

How should this be tested?

Test Scenario 1 - Managed user as HOST:

1. Create an event type using managed user's access token
2. Create booking on that event type (external user booking managed user)
3. GET /v2/bookings/{uid} with header Cal-Api-Version: 2024-08-13
4. Verify hosts[].email returns original email with suffix
5. Verify hosts[].displayEmail returns email without suffix

Test Scenario 2 - Managed user as ATTENDEE:

1. Create booking where attendee is a managed user
2. GET /v2/bookings/{uid} with header Cal-Api-Version: 2024-08-13
3. Verify attendees[].email returns original email with suffix
4. Verify attendees[].displayEmail returns email without suffix

Test Scenario 3 - Self-booking:

1. Managed user books their own event type
2. Verify both email and displayEmail fields are present and correct

Expected result: email fields preserve original value, displayEmail fields return clean email without +{cuid} suffix

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• 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. - N/A, OpenAPI spec auto-updated
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

Human Review Checklist

• Verify regex pattern /\+[a-zA-Z0-9]{25}/ correctly strips CUID suffixes without affecting normal emails
• Confirm backwards compatibility: original email field values are unchanged
• Verify displayEmail is added to all booking output types (hosts, attendees, reassignedTo)

Original PR URL: calcom#25593