Export apns:default_connection/0 to allow key file password to be added,...

... e.g.

%% Pull password from e.g. sys.config here
ConnectionProfile = (apns:default_connection())#apns_connection{cert_password=Password, error_fun=fun ?MODULE:handle_apns_error/2, feedback_fun=fun ?MODULE:handle_apns_feedback/2},
Connection = apns:connect(apns_connection, ConnectionProfile)

It's this approach vs. modifying default_connection/0 directly.  This is the least intrusive.