feat: add user centric features

migrations/0005_add_user_handle_and_plan.up.sql

@@ -0,0 +1,31 @@
+-- Adds the social-handle + subscription-plan columns to `users`.
+--
+--   handle  — case-insensitive (citext) URL slug, e.g. /u/satya-das.
+--             Auto-generated from the email-local part on signup; user can
+--             change it later via PATCH /users/me. Unique across the table.
+--   plan    — 'free' (default) or 'premium'. Controls limits enforced at
+--             the service layer (bookmarks count, collection counts).
+--             No checkout flow yet — admin flips it with SQL.
+ALTER TABLE users
+    ADD COLUMN IF NOT EXISTS handle CITEXT,
+    ADD COLUMN IF NOT EXISTS plan VARCHAR(16) NOT NULL DEFAULT 'free'
+        CHECK (plan IN ('free', 'premium'));
+
+-- Backfill handles for any rows that already exist. The recipe mirrors the
+-- generator the auth service uses: slugify the local-part of the email and
+-- append a 6-char random suffix to make collisions vanishingly unlikely.
+UPDATE users
+SET handle = LOWER(REGEXP_REPLACE(SPLIT_PART(email::text, '@', 1), '[^a-z0-9]', '', 'g'))
+             || '-' || substr(md5(id::text), 1, 6)
+WHERE handle IS NULL;
+
+ALTER TABLE users ALTER COLUMN handle SET NOT NULL;
+
+DO $$
+BEGIN
+    IF NOT EXISTS (
+        SELECT 1 FROM pg_constraint WHERE conname = 'users_handle_key'
+    ) THEN
+        ALTER TABLE users ADD CONSTRAINT users_handle_key UNIQUE (handle);
+    END IF;
+END$$;