Add functionality to add single addressee to tickets

This update introduces a new feature allowing end-users to add a single addressee to a ticket without removing the existing ones. This was achieved by adding a new API endpoint and updating the SetAddresseesController to handle the addition of a single addressee. Accompanying tests have also been provided to ensure the new feature works as expected.

src/Bundle/ChillTicketBundle/chill.api.specs.yaml

@@ -115,7 +115,7 @@ paths:
                         schema:
                             type: object
                             properties:
-                                addresses:
+                                addressees:
                                     type: array
                                     items:
                                         oneOf:
@@ -129,3 +129,35 @@ paths:
                 422:
                     description: "UNPROCESSABLE ENTITY"
 
+    /1.0/ticket/{id}/addressee/add:
+        post:
+            tags:
+                - ticket
+            summary: Add an addressee to a ticket, without removing existing ones.
+            parameters:
+                -   name: id
+                    in: path
+                    required: true
+                    description: The ticket id
+                    schema:
+                        type: integer
+                        format: integer
+                        minimum: 1
+            requestBody:
+                required: true
+                content:
+                    application/json:
+                        schema:
+                            type: object
+                            properties:
+                                addressee:
+                                    oneOf:
+                                        - $ref: '#/components/schemas/UserGroupById'
+                                        - $ref: '#/components/schemas/UserById'
+
+
+            responses:
+                201:
+                    description: "ACCEPTED"
+                422:
+                    description: "UNPROCESSABLE ENTITY"