API v2 delete alert filter

[Elise17]

Implement endpoint DELETE /api/v2/alerts-filters/{identifier} to delete an alert filter.

• return 204 in case of success
• create method in the business layer
• GET /api/v2/alerts-filters/{identifier} returns 404, after delete
• return an empty body in case of success
• return 404 when the alert filter is not found
• deprecate POST /filters/delete/{filter_id}
• openapi: document endpoint