Add peripheral didUpdateMTU method

[ladislas]

This is useful when MTU negotiation happens and the user needs the final value for app logic.

[klundberg]

Thanks for the contribution, must have missed that api. Could you fix the test compilation failures as well?

[ladislas]

@klundberg well actually not missed, it doesn't exist... I don't know where I got the idea, I thought I read it somewhere, wrote the code and it compiled. but there is actually no method func peripheral(_ peripheral: CBPeripheral, didUpdateMTU mtu: Int) in CBPeripheral/Delegate.

I wish there was though! I guess the only way to know the final MTU is to have our device share it through a dedicated characteristics when it's updated.

Sorry for the false hope :)

[klundberg]

No worries! I'm glad I didn't miss something potentially important after all, it is unfortunate that this isn't available if it would be useful though.