custom metadata in federation handshake

[DaniHaag]

My use case is, I want to define and set the instanceId for a client within an iframe from the outer frame. I did not find any place where to properly hook in to the federation process.

Is this a supported pattern? Or is there another way to implement the use case above.

My idea was that I could exchange custom data between the federated clients on the federation handshake. To reset the instanceId within the iframe two federation handshakes would be done. The first handshake is based on an arbitrary instanceId for the iframe and the outer frame would post the target instanceId for the iframe in the federation pong message that it's sending as part of the handshake. When the iframe part is called back on signalReady it would basically set the passed instanceId using postal.instanceId() function which results in the "instanceId.changed" message.

EDIT: I created an inital solution how this could be solved can be found on my fork on
https://github.com/DaniHaag/postal.federation