chore(deps): upgrade to postgres 18 and latest mattermost patch release

[brandon1024]

Summary

This revision bumps postgres from version 14 to the latest supported release, version 18. In version 18, the format of the persistent storage volume changed to improve ease of database upgrades. To accomodate this, the volume mounts for the postgres service in docker compose was adjusted. Refer to the upstream documentation for more details.

Additionally, mattermost was upgraded to the latest patch release 10.11.7 which includes some low- to medium-severity security fixes.

I've tested this in my personal environment for a few weeks, works well :-)

Ticket Link

None.

[brandon1024]

Just to offer a bit of background on this change, I had originally deployed mattermost in my environment using the old postgres version listed here, but eventually wanted to upgrade to stay ahead in the postgres release cycle. Upgrading postgres is a bit of a pain, but the changes introduced in version 18 of the upstream docker image will make that much easier going forward.

Important Change: the PGDATA environment variable of the image was changed to be version specific in PostgreSQL 18 and above⁠. For 18 it is /var/lib/postgresql/18/docker. Later versions will replace 18 with their respective major version (e.g., /var/lib/postgresql/19/docker for PostgreSQL 19.x). Mounts and volumes should be targeted at the updated location. This will allow users upgrading between PostgreSQL major releases to use the faster --link when running pg_upgrade and mounting /var/lib/postgresql.

I figured I'd contribute that back to the community so that future upgrades are either for all.

Thanks for the awesome platform, I've been really enjoying mattermost!

[mattermost-build]

This PR has been automatically labelled "stale" because it hasn't had recent activity.
A core team member will check in on the status of the PR to help with questions.
Thank you for your contribution!

[brandon1024]

Not stale -- just waiting for review from a maintainer :-)

/cc @amyblais

[NARSimoes]

Thank you for submitting the change. I just have a minor comment for clarification, but otherwise looks good.

[mattermost-build]

This PR has been automatically labelled "stale" because it hasn't had recent activity.
A core team member will check in on the status of the PR to help with questions.
Thank you for your contribution!

[brandon1024]

Still active, just awaiting review.

[mattermost-build]

This PR has been automatically labelled "stale" because it hasn't had recent activity.
A core team member will check in on the status of the PR to help with questions.
Thank you for your contribution!

[brandon1024]

Still active, just pending merge from maintainers.