Consider running Vector as a separate user inside Docker

It was proposed in the chat by @afoninsky to use a dedicated non-root user in Vector's Docker containers, in order to improve security.

The best practices for writing Dockerfiles recommend to create a separate user if the service inside the container can run without root privileges.

So I want to discuss here can all Vector's functions be used if Vector is running inside of a container from a non-root user. In particular, we need to ensure that both journald and docker sources can be used to read logs on the host machine from within a container when the user inside the container is not root.

Start by locating Vector's Dockerfile and container configuration, then inspect the journald and docker source implementations for their host-log access requirements. Verify whether both sources work under a dedicated non-root container user, and document or implement the required support and validation. The issue names no specific files or tests and remains an open design discussion.