[Enhancement] Pair with a device requiring an agent with the NoInputNoOutput capability

[barjonas]

Description

As a user, I'd like to pair with a device requiring an agent with the NoInputNoOutput capability. I believe this applies to most HIDs since they don't have a screen or a PIN.

I see a similar issue #34. I guess agents are the missing link there too.

What I've tried

With the default agent, I get this exception from PairAsync:

Tmds.DBus.DBusException: org.bluez.Error.AuthenticationFailed: Authentication Failed at Tmds.DBus.DBusConnection.CallMethodAsync(Message msg, Boolean checkConnected, Boolean checkReplyType) at Tmds.DBus.Connection.CallMethodAsync(Message message) at Tmds.DBus.CodeGen.DBusObjectProxy.SendMethodReturnReaderAsync(String iface, String member, Nullable`1 inSignature, MessageWriter writer)

Possible solution

Looking at the D-Bus API documentation, I guess the minimum implementation would require the agent manager (org.bluez.AgentManager1) to be wrapped and at least the RegisterAgent and RequestDefaultAgent methods. Does this sound right? Would you be want a pull request, even for a partial implementation?

Finally, I'd love to hear if there's a workaround, e.g. by running a non-.NET implementation in another process just to provide the agent.