Different ringtone when active call (multiple accounts)

[jsalvata]

We have a configuration with two accounts (with separate VoIP providers).

If we use a short and soft ringtone, we often miss calls (because we're not wearing the headset at all times). . If we use a long and loud ringtone, it stops us hearing the other party if a call gets in on one account while there's an active call on the other.

Possible solutions which occur to me: a) Allow configuring a 2nd ringtone to use while there's an active call (other products use a short "beep" to indicate a call is waiting). b) Show vistual indications but no ring for the 2nd call. c) Just deliver a BUSY signal on the 2nd call and don't ring.

(Unfortunately the two providers use very different user ids, so we can't use issue #172 as a workaround)