* RPC forwarders for adding reserved peers

* implement service side of reserved-peer RPCs

* Clean up unnecessary format! invocation

Co-Authored-By: Niklas Adolfsson <niklasadolfsson1@gmail.com>

* add some tests for the new RPC methods

* remove redundant `data` field

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>