Upgrade to Mattermost 10 ESR

[DavidePrincipi]

The current Mattermost v9.11 ESR goes out-of-support on 2025-05-15

https://docs.mattermost.com/about/mattermost-server-releases.html#latest-releases

• Upgrade to v10 ESR when it becomes available.
• PostgreSQL 13 will be EOL on 2025-11-13 https://www.postgresql.org/support/versioning/

[DavidePrincipi]

Mattermost 10.5 ESR has been released on 2025-02-16 and will be supported until 2025-11-15.
https://docs.mattermost.com/about/mattermost-v10-changelog.html#release-v10-5-extended-support-release

[gsanchietti]

Testing image: mattermost-2.2.0-dev.1

Test case 1: clean install

• Enable testing repository
• Install a new instance
• Configure and verify that Mattermost is correctly started

Test case 2: update

• Install a new instance from stable
• Configure the instance and write at least one message
• Update the instance to testing version: api-cli run update-module --data '{"module_url": "ghcr.io/nethserver/mattermost:2.2.0-dev.1", "instances": ["mattermost1"]}
• Verify the instance has been upgraded
• Access Mattermost instance and verify that messages are still there