Support for running under different user

[nijel]

I ended up giving up on running on a non-1000 UID and that allowed me to work around the ssh key issue.

IMO it'd be both cleaner for host filesystem mapping and also enhanced security if UID parameter was supported in the docker version.

Originally posted by @Skyedra in WeblateOrg/weblate#10037 (comment)

[github-actions]

This issue has been added to the backlog. It is not scheduled on the Weblate roadmap, but it eventually might be implemented.

In case you need this feature soon, please consider helping or push it by funding the development.