chore: use new database credentials by default

Use the new database credentials by default.

The `experimental.useNewDatabaseCredentials` feature flag can be removed
once it's been removed from all `build.yaml` files.

CHANGELOG.md

@@ -16,3 +16,4 @@
 * `App\Enum\Webserver` now returns a string.
 * `ConfigurationValidatorTest` no longer performs serialisation.
 * Use `set -o errexit` and `set -o pipefail` in `run` scripts instead of `set -eu`.
+* Use new database credentials by default.

resources/build.defaults.yaml

@@ -2,6 +2,6 @@ drupal:
   docroot: web
 
 experimental:
-  useNewDatabaseCredentials: false
+  useNewDatabaseCredentials: true
 
 project_root: /app

src/DataTransferObject/Config.php

@@ -109,6 +109,7 @@ final class Config
             'runGitHooksBeforePush' => new Assert\Optional([
                 new Assert\Type('bool'),
             ]),
+            // TODO: remove this when its been removed from all `build.yaml` files.
             'useNewDatabaseCredentials' => new Assert\Optional([
                 new Assert\Type('bool'),
             ]),