feat: implement user follow/unfollow functionality and thought retrieval by user

- Added follow and unfollow endpoints for users.
- Implemented logic to retrieve thoughts by a specific user.
- Updated user error handling to include cases for already following and not following.
- Created persistence layer for follow relationships.
- Enhanced user and thought schemas to support new features.
- Added tests for follow/unfollow endpoints and thought retrieval.
- Updated frontend to display thoughts and allow posting new thoughts.

thoughts-backend/tests/api/mod.rs

@@ -1,30 +1,5 @@
-use api::setup_router;
-use utils::testing::setup_test_db;
-
-mod root;
+mod feed;
+mod follow;
+mod main;
+mod thought;
 mod user;
-
-use root::*;
-use user::*;
-
-#[tokio::test]
-async fn root_main() {
-    let db = setup_test_db("sqlite::root?mode=memory&cache=shared")
-        .await
-        .expect("Set up db failed!");
-
-    let app = setup_router(db);
-    test_root(app).await;
-}
-
-#[tokio::test]
-async fn user_main() {
-    let db = setup_test_db("sqlite::user?mode=memory&cache=shared")
-        .await
-        .expect("Set up db failed!");
-
-    let app = setup_router(db);
-    test_post_users(app.clone()).await;
-    test_post_users_error(app.clone()).await;
-    test_get_users(app).await;
-}