API v2 create an object's comment

[c8y3]

Implement endpoint POST /api/v2/{object}/{object_identifier}/comments to create a comment, where object is any of alerts, assets, events, tasks, notes, evidences or iocs:

• return 201 in case of success
• should allow to set a field ('comment_text')
• check returned object is uniform with other endpoints
• if a required field is missing, return 400
• if a field value has the wrong type, return 400
• return 403 if the user is denied permission to create comment (no access to case or alert)
• if the underlying object is not found, return 404
• create method in the business layer
• deprecate POST /{object}/{object_identifier}/comments/add
• openapi: document endpoint
• openapi: deprecate POST /{object}/{object_identifier}/comments/add