Prepare support for Ubuntu 22.04 (Jammy)

[ddavness]

Ubuntu 22.04 (codename Jammy Jellyfish) is expected to be out on the 21st April - a month from today.

The bad news

Ubuntu 22.04 ships with PHP 8.1, which is essentially a big leap from PHP 7.4, and skipping over PHP 8.0 entirely. The latest Nextcloud release (NC 23) only supports PHP 8.0.

On the other hand, Nextcloud 24 does not support PHP 7.3 (ref nextcloud/server#29914). That means that support for Debian 10 (Buster) will need to be dropped.

Plan of action

There will be two releases of Power Mail-in-a-Box around this event:

• An interim release that will bring NextCloud to the latest version (NC 23);
• • Target release date: Sunday, 26th March
• An actual release that will bring NextCloud to major version 24. Ubuntu 22.04 will be supported, but Debian 10 will not support this release.
• • Target release date: Sunday, 1st May Wednesday, 1st June

[ddavness]

Actually - we're also depending on Roundcube 1.6 to become stable, as that's the first version that also happens to support PHP8.1 - therefore the target of 1st May may be missed entirely

[ddavness]

:tada: https://github.com/ddavness/power-mailinabox/releases/tag/v60.0