Token plugins provide a generic interface for transforming a token
into a `(host, port)` tuple.
The plugin name is specified using the '--token-plugin' option,
and may either be the name of a class from `websockify.token_plugins`,
or a fully qualified python path to the token plugin class (see below).
An optional plugin parameter can be specified using the '--token-source'
option (a value of `None` will be used if no '--token-source' option is
passed).
Token plugins should inherit from `websockify.token_plugins.BasePlugin`,
and should implement the `lookup(token)` method. The value of the
'--token-source' option is available as `self.source`.
Several plugins are included by default. The `ReadOnlyTokenFile`
and `TokenFile` plugins implement functionality from '--target-config'
(with the former only reading the file(s) once, and the latter reading
them every time). The 'BaseTokenAPI' plugin fetches the value from
an API, returning the result of `process_result(response_object)`.
By default, `process_result` simply returns the text of the response,
but may be overriden. The `JSONTokenAPI` does just this, returning
the 'host' and 'port' values from the response JSON object.
The old '--target-config' option is now deprecated, and maps to the
`TokenFile` plugin under the hood.
Also-Authored-By: James Portman (@james-portman)
Closes#157