Revert massive replacement of empty list creation sentences. The use of '[list]' instead of '{}' adds semantics that could be used for performance improvements in the future, such as using a different internal representation. There is already work in this direction, avoiding the generation of the string representation during comparison of empty strings (huge thanks to Stefan Sobernig for the pointer: https://core.tcl.tk/tcl/info/44527c632ed609c2).
change ad_verify_and_get_user_id to ad_conn user_id, change ad_maybe_redirect_for_registration to auth::require_login, make some db_ and dt_ function -public