feat(fixed-hosts): pick first host as organizer for collective events or round robbin with fixed hosts

[bandhan-majumder]

What does this PR do?

For collective events or round robin with fixed hosts, it sets first host is the default organizer. This adds a new attribute isOrganizer for the host entity to which is false by default

• Fixes [CAL-5348] Always pick first host as the organizer #20301 (GitHub issue number)
• Fixes CAL-5348 (Linear issue number - should be visible at the bottom of the GitHub issue description)

Visual Demo (For contributors especially)

Video Demo (if applicable):

organizer.mp4

Image Demo (if applicable):

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• I confirm automated tests are in place that prove my fix is effective or that my feature works.

How should this be tested?

• Are there environment variables that should be set?
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Checklist

• I haven't read the contributing guide
• My code doesn't follow the style guidelines of this project
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[cubic-dev-ai]

No issues found across 14 files

[bandhan-majumder]

calling this default organizer instead of organizer because of this line

https://github.com/bandhan-majumder/cal.com/blob/aa21d89e8e733f7fe7b2459312d5740869a95fb9/packages/features/bookings/lib/service/RegularBookingService.ts#L1267

this tells that if the request has a teamMemberEmail field, then the exact member will be the organizer. and if not, then we can pick the organizer of the event among the hosts as organizer if exists.

[bandhan-majumder]

One improvement that can be done is immediately showing the default organizer tag in the UI as soon as the first member gets added or the organizer gets removed (the earliest joiner is the organizer here) and invalidation happens. But here I tried to add form resetting logic but the current logic seem to be a bit complex and throwing type errors even though I regenerated the types.