Feat(API + Docs): Handle user sessions

- Improved documentation
- Wrote tests for user sessions/authentications: including session
  flow(login, status, logout)

backend/tests/blueprints/test_sessions.py

@@ -0,0 +1,24 @@
+from quart import Quart
+
+
+async def test_session_flow(app: Quart) -> None:
+    test_client = app.test_client()
+    await test_client.post(
+        "/sessions/",
+        json={"email": "member@todo.minhtrannhat.com", "password": "password"},
+    )
+    response = await test_client.get("/sessions/")
+    assert (await response.get_json())["memberId"] == 1
+    await test_client.delete("/sessions/")
+    response = await test_client.get("/sessions/")
+    assert response.status_code == 401
+
+
+async def test_login_invalid_password(app: Quart) -> None:
+    test_client = app.test_client()
+    await test_client.post(
+        "/sessions/",
+        json={"email": "member@todo.minhtrannhat.com", "password": "incorrect"},
+    )
+    response = await test_client.get("/sessions/")
+    assert response.status_code == 401