The responding side now relies on a new MetadataExtractor which decodes
metadata entries of interest, and adds them to an output map whose
values are then added as Message headers, and are hence accessible to
controller methods.
Decoded metadata entry values can be added to the output map one for
one, or translated to any number of values (e.g. JSON properties),
as long as one of the resulting pairs has a key called "route".
On the requesting side, now any metadata can be sent, and a String
route for example is not required to be provided explicitly. Instead
an application could create any metadata (e.g. JSON properties) as long
as the server can work out the route from it.
The commit contains further refinements on the requesting side so that
any mime type can be used, not only composite or routing metadata, e.g.
a route in an "text/plain" entry.
Closes gh-23157
5bf070a857