Add information about managing contrib modules along-side the upstream managed contrib modules to the README.

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Conditions of satisfaction

• Address why composer version constraint errors may occur when updating Quickstart.
• List the options for how to resolve version constraint errors.

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During the lifespan of a custom website on the Quickstart upstream, chances are you'll have a module or two installed that Arizona Digital decides to take over maintenance for within Quickstart.

Generally this is great news, you no longer need to deal with updates for that contrib module, however, at the moment relinquishing the maintenance burden is a manual process.

Troubleshooting

If you are unable to apply upstream updates via the dashboard, there is a possibility that the problem is a composer version constraint violation.

Quickstart's composer.json is likely conflicting with your site specific composer.json file for a specific package.

For example, if your site-specific composer.json file has "drupal/workbench_access": "1.1", within the require section and decide to upgrade from Quickstart 2.5.4 to Quickstart 2.6.0, you'll likely see a version constraint error and pantheon's integrated composer will fail to apply the update, since Arizona Digital took over maintenance responsibility for that module in 2.6.0 and has since updated it.

What can you do to solve this issue.

1. The easiest and usually best way to resolve this is to delete that module from your site specific composer.json file.

composer remove drupal/workbench_access

2. Use the version within your composer.json as the version in the upstream.

composer require "drupal/workbench_access: 1.1 as 2.1"