[FEATURE] Allow use variables in User Identifier

[estilles]

Describe the feature
At the moment, for actions that allow users to specify a username via the User Identifier option, one can only enter a literal string and cannot make user of Companion variables. This features allows users to do so.

Usecases
Allow consumers of this module to use variables in the User Identifier option of all actions that include this option. Below is an example of how I'm currently using it.

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I've already worked on this feature ... PR to follow.