feat: add avatar urls to groups (#4525)

coderd/database/migrations/000062_group_avatars.down.sql

@@ -0,0 +1,5 @@
+BEGIN;
+
+ALTER TABLE groups DROP COLUMN avatar_url;
+
+COMMIT;

coderd/database/migrations/000062_group_avatars.up.sql

@@ -0,0 +1,5 @@
+BEGIN;
+
+ALTER TABLE groups ADD COLUMN avatar_url text NOT NULL DEFAULT '';
+
+COMMIT;