[FEATURE] support for multiple iCloud users

[nicx]

Use case
As a family, I want to backup multiple iCloud users with only one docker instance of iCloud-docker so that I do not need to maintain multiple containers.

Describe the solution you'd like
As of today I am using one docker instance of iCloud-docker for each iCloud-user in my family. This is fine and works as expected. As an idea maybe its easier to use only one docker instance for that, which makes it more simple for the administrator of the docker containers :)

[github-actions]

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