qapi: add support to default value for optional members
Goal
Quoting Markus from the mailing list:
Extend the QAPI language to support optionals with a default value, i.e. absent is indistinguishable from present with the default value. Then use this for as many optionals as we can.
Technical details
To be defined.
Additional information
This is a proposal to the QAPI spec itself to have a simple way to express that an absent member defaults to a value.