feat: db self following migration

packages/db/prisma/migrations/20250331133341_remove_self_follows/migration.sql

@@ -0,0 +1,28 @@
+-- Remove follows where a user is following their own personal channel
+DELETE FROM "Follow" f
+USING "User" u
+WHERE f."userId" = u.id 
+  AND f."channelId" = u."personalChannelId"
+  AND u."personalChannelId" IS NOT NULL;
+
+-- Create a function to prevent self follows
+CREATE OR REPLACE FUNCTION prevent_self_follows()
+RETURNS TRIGGER AS $$
+BEGIN
+  IF EXISTS (
+    SELECT 1 FROM "User"
+    WHERE id = NEW."userId"
+      AND "personalChannelId" = NEW."channelId"
+      AND "personalChannelId" IS NOT NULL
+  ) THEN
+    RAISE EXCEPTION 'Users cannot follow their own personal channel';
+  END IF;
+  RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Create a trigger that uses this function
+CREATE TRIGGER check_self_follow
+BEFORE INSERT OR UPDATE ON "Follow"
+FOR EACH ROW
+EXECUTE FUNCTION prevent_self_follows();