Add support for colour attribute on allowances in backend (#77)

Closes #76

Reviewed-on: #77

backend/api_test.go

@@ -516,6 +516,7 @@ func TestPutAllowanceById(t *testing.T) {
 		"name":   TestAllowanceName,
 		"target": 5000,
 		"weight": 10,
+		"colour": "#FF5733",
 	}
 	resp := e.POST("/user/1/allowance").WithJSON(requestBody).Expect().Status(201).JSON().Object()
 	allowanceId := int(resp.Value("id").Number().Raw())
@@ -525,6 +526,7 @@ func TestPutAllowanceById(t *testing.T) {
 		"name":   "Updated Allowance",
 		"target": 6000,
 		"weight": 15,
+		"colour": "#3357FF",
 	}
 	e.PUT("/user/1/allowance/" + strconv.Itoa(allowanceId)).WithJSON(updateRequest).Expect().Status(200)
 
@@ -534,6 +536,7 @@ func TestPutAllowanceById(t *testing.T) {
 	result.Value("name").IsEqual("Updated Allowance")
 	result.Value("target").IsEqual(6000)
 	result.Value("weight").IsEqual(15)
+	result.Value("colour").IsEqual("#3357FF")
 }
 
 func TestCompleteTask(t *testing.T) {