Cumulative Drupal 9 Readiness Patches

Cumulative Drupal 9 Readiness Patches.

⚠ The following instructions still work, but are no longer necessary thanks to Drupal's new Lenient Composer Endpoint.

This MR combines all the Drupal 9 compatibility patches recommended by #3074066, #3073475, and #3129711.

It is useful to have an issue fork for Drupal 9 compatibility, rather than simply a patch, because:

In short, you can't use a patch to tell Composer that a Drupal 8 module is compatible with Drupal 9.

Source: https://www.mediacurrent.com/blog/how-fix-catch-22-problem-drupal-9-fixes-composer/

Adding Issue Fork as a Composer repository:

To use this issue fork as a transitional D9-compatible package in your project, modify your composer.json:

    "repositories": {
        "drupal/entity_activity": {
            "type": "vcs",
            "url": "https://git.drupalcode.org/issue/entity_activity-3129711"
        },
        "drupal": {
          "type": "composer",
          "url": "https://packages.drupal.org/8",
          "exclude": ["drupal/entity_activity"]
        },

Requiring the patched package from the Issue Fork:

Execute the following command in a terminal:

$ composer require drupal/entity_activity:dev-3129711-drupal-9-readiness

or manually add the requirement to composer.json:

    "require": {
        "drupal/entity_activity": "dev-3129711-drupal-9-readiness",

Credit due, mainly, to Benji Fisher via: https://www.drupal.org/project/views_url_alias/issues/3142138#comment-14177409

NOTE:

Instructions above tested (with Drupal 8.9.18) and patched module now passes Upgrade Status tests.

Not yet tested with Drupal 9. You can help the Drupal community by testing this! 👍

Closes #3129711 (unless you prefer my next Merge Request on the same Issue Fork)