allow setting the DisplayName property for newly provisioned peers (#507)

docs/documentation/rest-api/swagger.yaml

@@ -403,6 +403,12 @@ definitions:
         type: object
     models.ProvisioningRequest:
         properties:
+            DisplayName:
+                description: |-
+                    DisplayName is an optional name for the new peer.
+                    If unset, a default template value (e.g., "API Peer ...") will be assigned.
+                example: API Peer xyz
+                type: string
             InterfaceIdentifier:
                 description: InterfaceIdentifier is the identifier of the WireGuard interface the peer should be linked to.
                 example: wg0