What does this PR do?

Adds support for filtering round robin event type hosts via API v2. When hostSubsetIds is provided, only the specified hosts are considered for availability calculation and booking assignment.

This allows API consumers to request availability and create bookings for a specific subset of hosts within a round robin event type. For example, if a round robin event has 10 hosts but the user only wants to be matched with 2 specific hosts, they can pass those host IDs via hostSubsetIds.

Changes:

• Add hostSubsetIds to slots API input (GET /slots/available)
• Add hostSubsetIds to booking API input (POST /bookings)
• Update _findQualifiedHostsWithDelegationCredentials to filter by hostSubsetIds
• Pass hostSubsetIds through all layers: API → tRPC → slots/booking services

Requested by: [email protected] (@ThyMinimalDev)
Link to Devin run: https://app.devin.ai/sessions/c0fb075cea004bf58eb4cbec324781c5

Visual Demo (For contributors especially)

N/A - This is a backend API change with no UI components.

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• N/A I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. N/A - API docs are auto-generated from OpenAPI decorators.
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

How should this be tested?

1. Testing slots endpoint:

   • Create a round robin event type with multiple hosts
   • Call GET /v2/slots/available?eventTypeId={id}&startTime=...&endTime=...&hostSubsetIds=1,2
   • Verify only slots where hosts 1 or 2 are available are returned
   • If neither host 1 nor 2 exist in the event type, verify empty slots are returned

2. Testing booking endpoint:

   • Create a booking via POST /v2/bookings with hostSubsetIds: [1, 2]
   • Verify the booking is assigned to one of the specified hosts

3. Edge cases to verify:

   • hostSubsetIds with IDs that don't exist in the event type → should return empty availability
   • hostSubsetIds combined with routedTeamMemberIds → routedTeamMemberIds should filter within the hostSubsetIds subset

Checklist

• I have read the contributing guide
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have checked if my changes generate no new warnings

Human Review Checklist

• Verify the filtering order is intentional: hostSubsetIds is applied as a hard filter BEFORE contactOwnerEmail and routedTeamMemberIds filters
• Verify the "hard filter" behavior is desired - when hostSubsetIds results in no matching hosts, empty availability is returned (no fallback to all hosts)
• Consider if unit tests should be added for the new filtering logic in findQualifiedHostsWithDelegationCredentials.ts