feat(api): expand API endpoints for repo, PR, user, workspace management

- Add git operation endpoints: archive, compare branches, diff, tree,
  repository extras
- Add repo endpoints: contributors, delete fork, get branch/commit
  status/deploy key/invitation/member/release/tag/webhook, topics,
  release assets, webhook deliveries/retry
- Add PR endpoints: review requests, templates
- Add user endpoints: block/unblock, follow/unfollow, presence,
  personal access tokens, account restore
- Add workspace endpoints: billing history, approvals, domains,
  integrations, invitations, members, webhooks, restore
- Add internal API, notification API, IM API modules
- Update route configuration and OpenAPI spec

api/user/follow_user.rs

@@ -0,0 +1,47 @@
+use actix_web::{HttpResponse, web};
+use serde::Deserialize;
+use utoipa::IntoParams;
+
+use crate::api::response::{ApiErrorResponse, ApiResponse};
+use crate::error::AppError;
+use crate::models::users::UserFollow;
+use crate::service::AppService;
+use crate::session::Session;
+
+#[derive(Debug, Deserialize, IntoParams)]
+pub struct PathParams {
+    /// User ID to follow
+    pub target_user_id: uuid::Uuid,
+}
+
+/// Follow a user
+///
+/// Starts following the specified user. Requires authentication.
+#[utoipa::path(
+    post,
+    path = "/api/v1/user/follows/{target_user_id}",
+    tag = "User",
+    operation_id = "userFollowUser",
+    params(PathParams),
+    responses(
+        (status = 201, description = "User followed successfully.", body = ApiResponse<UserFollow>),
+        (status = 400, description = "Invalid request (e.g., following yourself)", body = ApiErrorResponse),
+        (status = 401, description = "Authentication required or session expired", body = ApiErrorResponse),
+        (status = 409, description = "Already following this user", body = ApiErrorResponse),
+        (status = 500, description = "Internal server error", body = ApiErrorResponse),
+    ),
+    security(
+        ("session_cookie" = [])
+    )
+)]
+pub async fn follow_user(
+    service: web::Data<AppService>,
+    session: Session,
+    path: web::Path<PathParams>,
+) -> Result<HttpResponse, AppError> {
+    let follow = service
+        .user
+        .user_follow_create(&session, path.target_user_id)
+        .await?;
+    Ok(HttpResponse::Created().json(ApiResponse::new(follow)))
+}