feat: Use container default user instead of forcing root user

[ma-04]

If a docker container has an user defined but run with user ID (--user=1000:1000) instead of user name, ofelia can encounter permission related issues with filesystem related tasks.

Also fixes the issue where all jobs were forced to run as root even when the container
had a different default user configured.

Initial testing shows working as expected when a docker container was started with --user restriction.

Changes:

• Change User field default from "root" to empty string in ExecJob, RunJob, and RunServiceJob
• Only set User in Docker API calls when explicitly specified by user
• Matches Docker's default behavior: no --user flag = container's default user

[ma-04]

@taraspos, any possibility of getting this merged or some feedback?

[taraspos]

Hi @ma-04,
Thanks for your PR, this is definitely something that we need to merge.

However, I'm worried about breaking change. A lot of people are using Ofelia and might be relying on current behaviour (don't get me wrong, using root by default is wrong and needs to be fixed), and I don't want to break their deployments out of the blue.

---

As it stands, there are currently two main versions of Ofelia - 0.3.x (or latest) and 0.4.x-beta.

If this PR is merged as is, it will become part of 0.4.x-beta, where having this breaking change is OK.
However, if you need/want this change as part of the existing 0.3.x, then we will need a separate, backward-compatible version of this change against the 0.3.x branch.

[ma-04]

Apologies for the late reply.

Ideally, I'd like to get this merged to latest. But I can understand the concern on this breaking workflow for users.

I will be doing some tests to see how it's behaving normally vs with the proposed changes, especially in terms of permission handling to see how it's impacting certain tasks and report back.

Thanks for your input again.

Edit: fix typo and clarify grammar