[REQ][docker container] default to uid 1000 + warn on output userid folder mismatch

Is your feature request related to a problem? Please describe.

when first using the docker based versions i was naively unaware and googled wrong to figure whats wrong,

going by the wrong advice i simply added :z to the volume spec

it was a very frustrating experience that only by chance resolved when i saw the user i switches

Describe the solution you'd like

for me ideally the docker containers for openapi would use the default user id of normal systems as a starting point,
and having the entry-point print a warning of the user ids owning the target folders differ from the active user ids

Describe alternatives you've considered

alternatively the README could have the example commands updated with -u "$(id -u):$(id -g)"

Inspect the Docker entry point and the README examples for the container commands, then reproduce a mounted output-folder ownership mismatch with the current user settings. Done means the container starts with UID 1000 by default, warns when target-folder ownership differs from the active user, or documents the required user mapping in the README.