feat: migrate imphnen-backend-hackathon into workspace as imphnen-hackathon crate

Consolidates the standalone hackathon backend (16 crates) into a single
imphnen-hackathon crate following the existing clean architecture patterns.
All endpoints are exposed under /v1/hackathon/ via the gateway.

Features migrated:
- Auth: Supabase-based signup/login/GitHub OAuth/password reset (own JWT)
- Users: profile management with team listing
- Teams: CRUD with city validation, deadline enforcement, invite system
- Invitations: team member invitations with accept/reject flow
- Join Requests: team join request workflow
- Chat: team messaging with author/leader delete permissions
- Submissions: project submission lifecycle (draft→pending→submitted)
- Storage: Supabase Storage file upload endpoints
- Certificates: public user certificate data endpoint
- Winners: public winners listing
- Admin: admin-only CRUD for all entities

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

imphnen-hackathon/src/join_requests/application/join_request_service.rs

@@ -0,0 +1,117 @@
+use std::sync::Arc;
+use uuid::Uuid;
+use async_trait::async_trait;
+use chrono::{Utc, TimeZone};
+use imphnen_utils::errors::AppError;
+use crate::join_requests::domain::entity::*;
+use crate::join_requests::domain::repository::JoinRequestRepository;
+use crate::join_requests::domain::service::JoinRequestService;
+
+fn is_team_features_closed() -> bool {
+    let deadline = Utc.with_ymd_and_hms(2025, 11, 30, 16, 59, 0).unwrap();
+    Utc::now() >= deadline
+}
+
+pub struct JoinRequestServiceImpl {
+    repo: Arc<dyn JoinRequestRepository>,
+}
+
+impl JoinRequestServiceImpl {
+    pub fn new(repo: Arc<dyn JoinRequestRepository>) -> Self {
+        Self { repo }
+    }
+}
+
+#[async_trait]
+impl JoinRequestService for JoinRequestServiceImpl {
+    async fn create_join_request(
+        &self,
+        team_id: Uuid,
+        user_id: Uuid,
+        input: CreateJoinRequestInput,
+    ) -> Result<JoinRequestWithDetails, AppError> {
+        if is_team_features_closed() {
+            return Err(AppError::BadRequestError(
+                "Join requests are closed (deadline: November 30, 2025).".to_string(),
+            ));
+        }
+        if !self.repo.team_exists(team_id).await? {
+            return Err(AppError::NotFoundError("Team not found".to_string()));
+        }
+        if self.repo.team_has_submission(team_id).await? {
+            return Err(AppError::BadRequestError("Cannot request to join a team that has already submitted".to_string()));
+        }
+        if let Some(active_team) = self.repo.user_active_team_name(user_id).await? {
+            return Err(AppError::ConflictError(format!("You are already a member of team '{}'", active_team)));
+        }
+        let count = self.repo.active_member_count(team_id).await?;
+        if count >= 5 {
+            return Err(AppError::BadRequestError("Team is already full (max 5 members)".to_string()));
+        }
+        if self.repo.pending_request_exists(team_id, user_id).await? {
+            return Err(AppError::ConflictError("You already have a pending request for this team".to_string()));
+        }
+        let id = Uuid::new_v4();
+        let entity = self.repo.create(id, team_id, user_id, &input.message).await?;
+        let details: Vec<JoinRequestWithDetails> = self.repo.find_by_user(user_id).await?;
+        details.into_iter().find(|r| r.id == entity.id)
+            .ok_or_else(|| AppError::InternalServerError("Failed to retrieve created join request".to_string()))
+    }
+
+    async fn get_my_join_requests(&self, user_id: Uuid) -> Result<Vec<JoinRequestWithDetails>, AppError> {
+        self.repo.find_by_user(user_id).await
+    }
+
+    async fn get_team_join_requests(
+        &self,
+        team_id: Uuid,
+        user_id: Uuid,
+    ) -> Result<Vec<JoinRequestWithDetails>, AppError> {
+        let leader_id = self.repo.get_team_leader_id(team_id).await?
+            .ok_or_else(|| AppError::NotFoundError("Team not found".to_string()))?;
+        if leader_id != user_id {
+            return Err(AppError::ForbiddenError("Only the team leader can view join requests".to_string()));
+        }
+        self.repo.find_pending_by_team(team_id).await
+    }
+
+    async fn respond_to_join_request(
+        &self,
+        request_id: Uuid,
+        user_id: Uuid,
+        accept: bool,
+    ) -> Result<(), AppError> {
+        let request = self.repo.find_by_id(request_id).await?
+            .ok_or_else(|| AppError::NotFoundError("Join request not found".to_string()))?;
+        let leader_id = self.repo.get_team_leader_id(request.team_id).await?
+            .ok_or_else(|| AppError::NotFoundError("Team not found".to_string()))?;
+        if leader_id != user_id {
+            return Err(AppError::ForbiddenError("Only the team leader can respond to join requests".to_string()));
+        }
+        if request.status != "pending" {
+            return Err(AppError::BadRequestError("Join request is no longer pending".to_string()));
+        }
+        if accept {
+            if is_team_features_closed() {
+                return Err(AppError::BadRequestError("Team features are now closed".to_string()));
+            }
+            if self.repo.team_has_submission(request.team_id).await? {
+                return Err(AppError::BadRequestError("Cannot accept join request after submitting a project".to_string()));
+            }
+            if let Some(active_team) = self.repo.user_active_team_name(request.user_id).await? {
+                return Err(AppError::ConflictError(format!("User is already a member of team '{}'", active_team)));
+            }
+            let count = self.repo.active_member_count(request.team_id).await?;
+            if count >= 5 {
+                return Err(AppError::BadRequestError("Team is already full".to_string()));
+            }
+            self.repo.update_status(request_id, "accepted").await?;
+            self.repo.add_team_member(request.team_id, request.user_id).await?;
+            self.repo.reject_pending_invitations_for_user(request.user_id).await?;
+            self.repo.reject_other_pending_for_user(request.user_id, request_id).await?;
+        } else {
+            self.repo.update_status(request_id, "rejected").await?;
+        }
+        Ok(())
+    }
+}