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/doc/src/thought.rs

@@ -0,0 +1,18 @@
+use api::{
+    models::{ApiErrorResponse, ParamsErrorResponse},
+    routers::thought::*,
+};
+use models::{params::thought::CreateThoughtParams, schemas::thought::ThoughtSchema};
+use utoipa::OpenApi;
+
+#[derive(OpenApi)]
+#[openapi(
+    paths(thoughts_post, thoughts_delete),
+    components(schemas(
+        CreateThoughtParams,
+        ThoughtSchema,
+        ApiErrorResponse,
+        ParamsErrorResponse
+    ))
+)]
+pub(super) struct ThoughtApi;