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/api/src/extractor/auth.rs

@@ -0,0 +1,29 @@
+use axum::{
+    extract::FromRequestParts,
+    http::{request::Parts, StatusCode},
+};
+
+use app::state::AppState;
+
+// A dummy struct to represent an authenticated user.
+// In a real app, this would contain user details from a validated JWT.
+pub struct AuthUser {
+    pub id: i32,
+}
+
+impl FromRequestParts<AppState> for AuthUser {
+    type Rejection = (StatusCode, &'static str);
+
+    async fn from_request_parts(
+        _parts: &mut Parts,
+        _state: &AppState,
+    ) -> Result<Self, Self::Rejection> {
+        // For now, we'll just return a hardcoded user.
+        // In a real implementation, you would:
+        // 1. Extract the `Authorization: Bearer <token>` header.
+        // 2. Validate the JWT.
+        // 3. Extract the user ID from the token claims.
+        // 4. Return an error if the token is invalid or missing.
+        Ok(AuthUser { id: 1 }) // Assume user with ID 1 is always authenticated.
+    }
+}

thoughts-backend/api/src/extractor/mod.rs

@@ -1,5 +1,7 @@
+mod auth;
 mod json;
 mod valid;
 
+pub use auth::AuthUser;
 pub use json::Json;
 pub use valid::Valid;