chore: create the test database on ddev start

.ddev/config.yaml

@@ -305,3 +305,11 @@ corepack_enable: false
 ## Un-comment to consume async message.
 #    post-start:
 #    - exec: symfony run --daemon --watch=config,src,templates,vendor bin/console messenger:consume async -vv
+
+# DDEV's `db` user may only touch the `db` database, so `doctrine:database:create` cannot make
+# the `_test` database that `when@test`'s dbname_suffix points at -- it fails with "Access
+# denied". Create it as root on every start instead, and hand the `db` user rights to it, so a
+# fresh checkout can run `vendor/bin/phpunit` without any manual setup.
+hooks:
+  post-start:
+    - exec: mysql -uroot -proot -hdb -e "CREATE DATABASE IF NOT EXISTS db_test CHARACTER SET utf8mb4; GRANT ALL ON db_test.* TO 'db'@'%'; FLUSH PRIVILEGES;"