Implement PUT /user/{userId}/allowance/{allowanceId} (#52)

Closes #17

Reviewed-on: #52

backend/dto.go

@@ -44,6 +44,12 @@ type CreateAllowanceRequest struct {
 	Weight int    `json:"weight"`
 }
 
+type UpdateAllowanceRequest struct {
+	Name   string `json:"name"`
+	Target int    `json:"target"`
+	Weight int    `json:"weight"`
+}
+
 type CreateGoalResponse struct {
 	ID int `json:"id"`
 }