Add endpoint to add funds (#99)

Closes #91

Reviewed-on: #99

backend/dto.go

@@ -73,3 +73,8 @@ type CreateTaskRequest struct {
 type CreateTaskResponse struct {
 	ID int `json:"id"`
 }
+
+type AddAllowanceAmountRequest struct {
+	Amount      float64 `json:"amount"`
+	Description string  `json:"description"`
+}