auto-populate missing username field with email local-part

prisma/migrations/20260317081600_normalize_user_emails/migration.sql

@@ -0,0 +1,2 @@
+-- This migration was generated locally but superseded before it was applied.
+-- It remains as a no-op to preserve Prisma migration history.

prisma/migrations/20260317103000_make_username_required_unique/migration.sql

@@ -0,0 +1,27 @@
+UPDATE users
+SET username = lower(split_part(email, '@', 1))
+WHERE username IS NULL OR btrim(username) = '';
+
+WITH ranked_users AS (
+  SELECT id,
+         username,
+         row_number() OVER (PARTITION BY username ORDER BY created_at, id) AS rn
+  FROM users
+),
+deduplicated AS (
+  SELECT id,
+         CASE
+           WHEN rn = 1 THEN username
+           ELSE left(username, greatest(1, 24 - char_length(rn::text))) || rn::text
+         END AS next_username
+  FROM ranked_users
+)
+UPDATE users u
+SET username = d.next_username
+FROM deduplicated d
+WHERE u.id = d.id;
+
+ALTER TABLE users
+ALTER COLUMN username SET NOT NULL;
+
+CREATE UNIQUE INDEX users_username_key ON users (username);

prisma/migrations/20260317110000_normalize_user_emails/migration.sql

@@ -1,8 +1,19 @@
+DO $$
+BEGIN
+  IF EXISTS (
+    SELECT 1
+    FROM (
+      SELECT LOWER(TRIM("email")) AS normalized_email
+      FROM "users"
+      GROUP BY LOWER(TRIM("email"))
+      HAVING COUNT(*) > 1
+    ) duplicates
+  ) THEN
+    RAISE EXCEPTION
+      'Cannot normalize user emails: duplicate values would conflict after lowercasing/trimming';
+  END IF;
+END $$;
+
 UPDATE "users"
 SET "email" = LOWER(TRIM("email"))
 WHERE "email" <> LOWER(TRIM("email"));
-
-ALTER TABLE "users"
-  DROP CONSTRAINT IF EXISTS "users_email_key";
-
-CREATE UNIQUE INDEX "users_email_key" ON "users"(LOWER("email"));