Add Service Desk Ticket as a new Work Item type to DB

What does this MR do and why?

Adds a service desk ticket as a new work item type.

Based on this spike: !121303 (closed)

Migration

Migration uses !127917 (merged) as an example.

db:migrate

→ be rails db:migrate
main: == [advisory_lock_connection] object_id: 225140, pg_backend_pid: 18731
main: == 20230804053643 AddTicketWorkItemType: migrating ============================
main: == 20230804053643 AddTicketWorkItemType: migrated (0.0729s) ===================

main: == [advisory_lock_connection] object_id: 225140, pg_backend_pid: 18731
ci: == [advisory_lock_connection] object_id: 225420, pg_backend_pid: 18733
ci: == 20230804053643 AddTicketWorkItemType: migrating ============================
ci: -- The migration is skipped since it modifies the schemas: [:gitlab_main].
ci: -- This database can only apply migrations in one of the following schemas: [:gitlab_ci, :gitlab_internal, :gitlab_shared].
ci: == 20230804053643 AddTicketWorkItemType: migrated (0.0135s) ===================

ci: == [advisory_lock_connection] object_id: 225420, pg_backend_pid: 18733

db:rollback

→ be rails db:rollback:main; be rails db:rollback:ci
main: == [advisory_lock_connection] object_id: 224720, pg_backend_pid: 19276
main: == 20230804053643 AddTicketWorkItemType: reverting ============================
main: == 20230804053643 AddTicketWorkItemType: reverted (0.0044s) ===================

main: == [advisory_lock_connection] object_id: 224720, pg_backend_pid: 19276


ci: == [advisory_lock_connection] object_id: 224680, pg_backend_pid: 19719
ci: == 20230804053643 AddTicketWorkItemType: reverting ============================
ci: -- The migration is skipped since it modifies the schemas: [:gitlab_main].
ci: -- This database can only apply migrations in one of the following schemas: [:gitlab_ci, :gitlab_internal, :gitlab_shared].
ci: == 20230804053643 AddTicketWorkItemType: reverted (0.0090s) ===================

ci: == [advisory_lock_connection] object_id: 224680, pg_backend_pid: 19719

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.