I'm looking for a way to generate a Conference resource within the Twilio system before adding anyone to that conference.
The official recommended way to start a Conference is by returning TwilXML in response to a Twilio callback. This can either be done in response to someone calling a Twilio number or, in a somewhat indirect way, by making a call and returning TwilXML which will connect the person to a conference once they pick up. All of the APIs to modify conferences use the ConferenceSID as the handle to decide what conference to change. The problem with both of these methods is that they do not give you the ConferenceSID until you receive a callback.
Unfortunately callbacks do not contain any identifying information about who generated them. They do have a ConferenceSID (identifying the conference), and a CallSID (uniquely identifying the call connecting the caller to the conference). When you get your first callback, there appears to be no way to be able to match either of those identifiers. If you start multiple conferences and get two callbacks with different ConferenceSIDs and different CallSIDs, it is inconvenient to tell which conference is generating which callback.
That's why it would be easiest to create a conference resource and then use the versatile add participant call. This would simplify the entire backend flow for using conferences by starting with the ConferenceSID and going from there.
P.s. To head off other suggestions - there are ways around this. You can specify different callback URLs for different conferences. You can specify different friendlyNames for different participants which you can match in your backend. It's totally possible to work with, but I would like something cleaner, which would require making conferences before anyone is called.
Twilio developer evangelist here.
There is no way to create a conference resource from the API. You can only do so by directing a caller there with the <Dial><Conference> TwiML.
Further, I don't quite understand when you say "When you get your first callback, there appears to be no way to be able to match either of those identifiers." What are you trying to match? You could use the CallSid to look up the From number of the caller joining the conference. You also receive the FriendlyName in the callback, which is the name you set in the TwiML <Conference>Friendly Name</Conference> which you could choose to help determine which conference is which.
Does that help at all?