[RFC] Credential agent interface

[Luiz Augusto von Dentz]

Hi Dirk,

If you check connman, BlueZ, obexd, you will find out how an dbus
agent works. They are meant for 'credentials' already since you can't
use signals because they provide no feedback (no error/reply). If you
depend just on signals:

1. you will loose the ability to detect if there is any process that
can provide credentials
2. you won't be able to react on process responsible for credential
disconnecting from bus
2. no implicit timeout
3. anyone can reply and multiple replies can happen which are tricky
to define a good strategy who to trust

In the other hand you may have a bigger problem since the
agent/process responsible for credentials will probably be either
connman or NetworkManager and both already have their own mechanisms
to collect credentials which could cause some problems such as NoReply
error. Although I expect connman to work it out since its storage is
accessible on the daemon which is not the case on NM that needs to
access its agents.


-- 
Luiz Augusto von Dentz
Engenheiro de Computação