GET /api/v1/target/ # return targets list
POST /api/v1/target/ # creates a new target group
GET /api/v1/target/<target_group_id> # retrieves the target group
PUT /api/v1/target/<target_group_id>/label # add a label or server to target group
PATCH /api/v1/target/<target_group_id>/label/<label_key> # updates a label in a target group
DELETE /api/v1/target/<target_group_id>/label/<label_key> # deletes a label in a target group
DELETE /api/v1/target/<target_group_id>/server/<server_id> # deletes a server in a target group