Allow to turn off Service Desk thank_you email per project

Proposal

Especially once Create Service Desk issue programmatically (#7042 - closed) has been implemented, customers might not need the initial thank_you email that Service Desk sends out upon issue/ticket creation. If our customers build integrations into their apps they might want to handle the initial response from their system.

Add an option to disable the thank_you email for a given project once we can create Service Desk issues via API.