Return more details when a transaction path for an intent could not be found

[sohkai]

Right now, we simply return an empty array when no transaction path was found.

Returning more data, like the intended to address and parameters would help UIs display more information, like which app or action they couldn't access.

[0xGabi]

Related to #219

[kernelwhisperer]

In the CLI we show: Cannot find transaction path for executing action

But we could show: ${account} is not permitted to perform the action ${action} on the app ${app}.

And then perhaps: Only the following entities can perform ${action}: ${app1}, ${account2}, etc. or Nobody can perform the action ${action}. You must first initialize the permission.

I can tackle this, any tips/ideas?

Should it throw an error with these messages?

[sohkai]

Hmm, the problem with just throwing an error is that most clients of the wrapper react on one of the observables firing.

Perhaps we could add more information to the this.transactions observable on each emission, like intended target and reason no path was found.