* guix/channels.scm (<channel-introduction>): Rename constructor to
'%make-channel-introduction'.
(make-channel-introduction): New procedure.
* tests/channels.scm ("authenticate-channel, wrong first commit signer")
("authenticate-channel, .guix-authorizations"): Use
'make-channel-introduction' without '@@' and without third argument.
* doc/guix.texi (Channels)[Channel Authentication, Specifying Channel
Authorizations]: New subsections.
8b7d982e6a