Allow to set user and password using environment variables at runtime

[laurentlemercier]

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Description

Allow to set user (at init) and password using an environment variable.
When used for init, need to restart docker container.

Fixes #(issue)
#194 (for example)

Type of change

Extension of reset-password.ts :
Set User and Password at init (container restart needed) :

docker exec -e USER=value1 -e PASSWORD=value2 -it dockge npm run reset-password
docker restart dockge

Just to set password (no restart needed):

docker exec --e PASSWORD=value2 -it dockge npm run reset-password

Please delete any options that are not relevant.

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

Checklist

• My code follows the style guidelines of this project
• I ran ESLint and other linters for modified files
• I have performed a self-review of my own code and tested it
• I have commented my code, particularly in hard-to-understand areas
  (including JSDoc for methods)
• My changes generate no new warnings
• [ x] My code needed automated testing. I have added them (this is optional task)

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