Support for setting uid and gid

[bimtauer]

For other languages testcontainers seems to support the option of customising the user that the container runs as (see e.g. NodeJS).

This is useful when using volume mounts in some controlled environment for example Github Actions. Without being able to set the uid to 1001 in github actions, files produced by a testcontainer cannot be opened due to filesystem permissions.

I assume the way to do this would be adding with_user to image_ext.rs.

I might be able to give this a try but wanted to check first here if this is a desired feature and if someone is maybe already on it.

[mervyn-mccreight]

I think this sounds like a useful feature 👍
AFAIK nobody is working on something like it, so we'd be very happy about a contribution from your side!