Summary of changes

• Updated the assignment flow to support inviting people by email.

• If an email does not belong to an existing team member, the user is automatically invited to the team as a Member.

• Added support for multiple emails, using comma-separated input (user1@example.com, user2@example.com).

• Updated frontend and backend to handle new host format { email, isPending } in addition to { userId }.

Why this is useful

• Makes it easier to quickly assign event-types to new collaborators without requiring them to be manually added to the team first.

• Supports inviting multiple participants in a single step, improving workflow efficiency.

Notes

• This PR only covers the basic invitation + assignment flow.

CI should validate tests, but feedback on edge cases (e.g., invalid emails, already invited users) would be appreciated.

Bounty

/claim #13532