Add put task endpoint (#33)

Closes #23

Reviewed-on: #33

backend/api_test.go

@@ -357,3 +357,31 @@ func TestGetTaskBadId(t *testing.T) {
 	createTestTask(e)
 	e.GET("/task/invalid").Expect().Status(400)
 }
+
+func TestPutTaskModifiesTask(t *testing.T) {
+	e := startServer(t)
+	createTestTask(e)
+	requestBody := map[string]interface{}{
+		"name":   "Updated Task",
+		"reward": 100,
+	}
+	e.PUT("/task/1").WithJSON(requestBody).Expect().
+		Status(200).
+		JSON().Object()
+
+	// Verify the task is updated
+	result := e.GET("/task/1").Expect().Status(200).JSON().Object()
+	result.Value("id").IsEqual(1)
+	result.Value("name").IsEqual("Updated Task")
+	result.Value("reward").IsEqual(100)
+}
+
+func TestPutTaskInvalidTaskId(t *testing.T) {
+	e := startServer(t)
+	createTestTask(e)
+
+	requestBody := map[string]interface{}{
+		"name": "Updated Task",
+	}
+	e.PUT("/task/999").WithJSON(requestBody).Expect().Status(404)
+}