#3496929 Opt in to Max PHP, manual if not downstream

Closes #3496929

.gitlab-ci.yml

@@ -16,8 +16,18 @@ variables:
   # Broaden test coverage.
   OPT_IN_TEST_PREVIOUS_MAJOR: 1
   OPT_IN_TEST_NEXT_MAJOR: 1
-#  OPT_IN_TEST_MAX_PHP: 1
+  OPT_IN_TEST_MAX_PHP: 1
   # Show more log output
   # _PHPUNIT_EXTRA: --verbose
   # Convenient, and we have no secrets.
   _SHOW_ENVIRONMENT_VARIABLES: 1
+
+composer (max PHP version):
+  rules:
+    - !reference [ .opt-in-max-php-rule ]
+    - !reference [ .check-max-php-version-rule ]
+    # Run automatically if part of a downstream pipeline. Otherwise manual.
+    - if: $CI_PIPELINE_SOURCE == 'pipeline'
+    # Using when: manual needs 'allow failure: true' otherwise the overall pipeline status shows 'blocked'
+    - when: manual
+      allow_failure: true