Sends a JSON body with the caller's headers to a registered address, as
deliverForm() sends a form.
Never rejects.
the entry carrying the address under attribute
the attribute holding the address, one of SENDABLE
the value sent as JSON
extra request headers, e.g. a Bearer token
Optionaloptions: DeliverOptions
timeoutMs and keepBody
a promise of the delivery result
Forwards to
FederationHttp.deliverJson().