add email query support

[pille]

please add a query for getting the email address from DB, like get_display_name does for the full name.
my usecase: prefill profile from DB

[alexeyabel]

What do you mean by "add a query"? Is this part of the Nextcloud user API? Please explain what exactly do you need.

[pille]

let the admin configure a sql query to retrieve a users email from DB. user settings contain an "Email"-field, which should be populated by that query-result.

[alexeyabel]

A clean implementation of this is, currently not possible, due to how user backends in Nextcloud work, see: #26 (comment)

[kosli]

@PanCakeConnaisseur Thanks for the update. I hope that the new user backend API (#7) will be implemented soon.