Per-mode (or global) access gate inside the source block.
access declarations live alongside actor_key and master_check
inside MishkaGervaz.Form.Dsl.Source. Each entry decides whether a
given form mode (:create or :update) is reachable for the current
user.
Three calling styles are supported:
# Style A — per-mode with keyword opts
access :create, restricted: true
# Style B — per-mode with condition function
access :create, fn state -> state.master_user? end
# Style C — global gate (`fn mode, state -> bool` in the mode slot)
access fn mode, state -> mode == :update or state.master_user? endStyle C is the catch-all: it runs for every mode and is useful when
you want one rule covering both :create and :update.
See MishkaGervaz.Form.Dsl.Source for the surrounding section.