Implement get goals (#25)

Closes #13

Reviewed-on: #25

backend/api_test.go

@@ -40,3 +40,19 @@ func TestGetUserBadId(t *testing.T) {
 	e := startServer(t)
 	e.GET("/user/bad-id").Expect().Status(400)
 }
+
+func TestGetUserGoalsWhenNoGoalsPresent(t *testing.T) {
+	e := startServer(t)
+	result := e.GET("/user/1/goals").Expect().Status(200).JSON().Array()
+	result.Length().IsEqual(0)
+}
+
+func TestGetUserGoalsNoUser(t *testing.T) {
+	e := startServer(t)
+	e.GET("/user/999/goals").Expect().Status(404)
+}
+
+func TestGetUserGoalsBadId(t *testing.T) {
+	e := startServer(t)
+	e.GET("/user/bad-id/goals").Expect().Status(400)
+}