add invite system

app/schema.py

@@ -90,6 +90,12 @@ SCHEMA = [
     "key" TEXT NOT NULL UNIQUE
     )""",
 
+    """CREATE TABLE IF NOT EXISTS "invite_keys" (
+    "id" INTEGER NOT NULL PRIMARY KEY,
+    "created_by" REFERENCES users(id) ON DELETE CASCADE,
+    "key" TEXT NOT NULL UNIQUE
+    )""",
+
     # INDEXES
     "CREATE INDEX IF NOT EXISTS idx_post_history_post_id ON post_history(post_id)",
     "CREATE INDEX IF NOT EXISTS idx_posts_thread ON posts(thread_id, created_at, id)",