pub fn record_dtmf(state: &State, digit: char)Expand description
Record one DTMF keypress into session state under the shared keys.
Sets KEY_DTMF to the digit and appends it to KEY_DTMF_HISTORY —
the exact writes every connector must make, factored to one place. While
the keypad is masked (KEY_KEYPAD_MASK) the digit goes to the
sensitive KEY_KEYPAD_ENTRY instead, and # ends the entry.