Pluggable transports are programs that disguise Tor traffic, which
can be useful in case Tor is censored. Pluggable transports
cannot be configured by #:config-file file exclusively because Tor
process is run via 'least-authority-wrapper' and cannot have access
to transport plugin, which is a separate executable (Bug#70302,
Bug#70332).
* doc/guix.texi (Networking Services): Document 'tor-transport-plugin'
data type and 'transport-plugins' option for 'tor-configuration.
* gnu/services/networking.scm: Export
'tor-configuration-transport-plugins', 'tor-transport-plugin',
'tor-transport-plugin?', 'tor-plugin-role',
'tor-plugin-protocol', and 'tor-plugin-program'.
(<tor-configuration>): Add 'transport-plugins' field.
(<tor-transport-plugin>): New variable.
(tor-configuration->torrc): Add content to 'torrc' computed-file.
(tor-shepherd-service): Add file-system-mapping(s).
Change-Id: I1b0319358778c7aee650bc843e021a6803a1cf3a
Signed-off-by: Ludovic Courtès <ludo@gnu.org>