Create dedicated Docker 'scraper' user

[kelson42]

Fixes #995

[kelson42]

@rgaudin This is an attempt to make our Docker a bit more secure. But this has for direct consequence that the mounted volumed should be writeable by the new user scraper. Not sure as well about the Redis daemon... which user runs it? Should we change it?

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be now be reviewed manually. Thank you for your contributions.

[codecov]

Codecov Report

Merging #1321 (d945025) into master (ebb737e) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1321   +/-   ##
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  Coverage   69.42%   69.42%           
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  Files          26       26           
  Lines        2401     2401           
  Branches      469      469           
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  Hits         1667     1667           
  Misses        569      569           
  Partials      165      165           

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[rgaudin]

• most rootless images defaults to user 1001 as this is what a regular distro would create so it has more chances to work out of the box.
• rootless implies choosing a user so uid and gid might be anything
• /data is gonna be mounted and there's no guarantee you'll be able to write on it. You may want to check that in entrypoint to provide a quick and clear feedback should permissions not be adequate. I don't know how quick and clear mwoffliner is gonna fail in this case.
• README may need to be updated to inform about write requirements on mounted volume source.

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be now be reviewed manually. Thank you for your contributions.