Install metatag_views: varbase_admin_base ships views using metatag_display_extender and nothing installs the submodule that provides it

Problem/Motivation

varbase_admin_base ships two views that declare the metatag_display_extender display extender:

• config/views.view.content.yml
• config/views.view.user_admin_people.yml

That plugin is provided by the metatag_views submodule of drupal/metatag, and no recipe in the chain installs it.

This recipe is the right place to fix it: it requires drupal/metatag: ~2 and already installs eight metatag submodules (metatag, eca_metatag, metatag_facebook, metatag_google_plus, metatag_hreflang, metatag_mobile, metatag_open_graph, metatag_twitter_cards, metatag_verification) — but not metatag_views. varbase_admin_base does not require drupal/metatag at all, so it cannot own this.

On a Varbase install the gap is hidden, because the install profile enables the submodule. On a Drupal CMS base nothing does, and building a view fatals:

Drupal\Component\Plugin\Exception\PluginNotFoundException:
The "metatag_display_extender" plugin does not exist.
Valid plugin IDs for Drupal\views\Plugin\ViewsPluginManager are: default

drupal_cms_seo_tools installs metatag but not this submodule either.

Steps to reproduce

1. Build a Drupal CMS 2.x site on Drupal core 11.4.5.
2. Require and install a Varbase site template that applies these recipes (tested with drupal/educare:1.0.x-dev).
3. Any page build touching the shipped views fatals with the exception above.
4. metatag_views is present at web/modules/contrib/metatag/metatag_views but never enabled.

Proposed resolution

Add metatag_views to this recipe's install: list, beside the other metatag submodules.

Verified on a Drupal CMS build: with the module installed, metatag_views is enabled and the exception is gone.

One ordering note for reviewers: this recipe applies later in a site template chain than varbase_admin_base, which is what imports the two views. That is fine, because a display extender plugin is only needed when a view is executed, not when its config is saved. If a future failure shows the plugin is needed earlier, that is a separate ordering question rather than a reason to move the dependency to a recipe that does not require metatag.

Remaining tasks

• ✅ File an issue
• ❌ Addition/Change/Update/Fix
• ❌ Testing to ensure no regression
• ➖ Automated unit/functional testing coverage
• ➖ Developer Documentation support
• ➖ User Guide Documentation support
• ➖ UX/UI designer responsibilities
• ➖ Accessibility and Readability
• ❌ Reviewed by a human
• ❌ Code review by maintainers
• ❌ Full testing and approval
• ❌ Credit contributors
• ❌ Review with the product owner
• ❌ Update Release Notes
• ❌ Release

User interface changes

• The Metatag tab becomes available on views, as intended by the shipped view config.

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• The Metatag Views submodule is now installed, so the views shipped by Varbase work on a Drupal CMS base.