Use user profile information in variables in office documents

Is your feature request related to a problem? Please describe.
In MS Office, it is possible to create an author profile for users, from which variables are filled. This is usually used in a "sidebar" or in the "footer" of a document to insert information like name, address, telephone number and email address. For public administration or bigger companies, sometimes an office number is also added (where the person works). This is not yet possible with Nextcloud.

Describe the solution you'd like
Right now it is possible to define form fields, which can be filled through Windmill or the API. If we used some pre defined variables here to access the data from the user profile, the requirement could be met.

Describe alternatives you've considered
Documents could be created through Windmill in almost the same way, but this is way more complicated than in MS Office.

Additional context
This feature is used a lot in public administration.

Begin with the existing form fields exposed through Windmill or the API and identify how user profile data is represented. Define supported profile variables for the requested name, address, telephone, email, and office number, then verify that they populate office-document fields; the issue names no implementation files or tests.