Multiple enhancements to MySQL, especially on Azure:
Nextcloud generates the config with database settings the first time that it is run, but from then on it does not automatically update the variables from the environment. This is a real pain if the password or hostname of the DB server needs to change, because an admin has to update the credentials in BOTH the environment AND the config volume, which is often mounted read-only. So, to support closer to a zero downtime deployment model for database connection string changes, this new config snippet should keep the database connection info in sync with the environment on a read-only config folder, even if what's in the config file is not in sync.
Adds the Azure DigiCert Global root CA that is needed to support MySQL Flexible server (since MariaDB is deprecated on Azure).
Multiple enhancements to MySQL, especially on Azure: