rest support in dynamic urls

[amitu]

In dynamic URLs we support basic types like string, integer etc, but they only capture one "part" of the path, part being what is delimited by /.

-- fastn.dynamic-urls:

url: /ide/<string:slug>/<string:f1>/
document: https://www.fifthtry.com/ide/index.ftd

We want to be able to support "rest of the url" as well, e.g.:

-- fastn.dynamic-urls:

url: /ide/<rest:name>
document: /ide/index.ftd

Here we are creating a new "virtual type" rest, which can be used for rest of the URL, and will be assigned to name in this case.

Note that:

-- fastn.dynamic-urls:

url: /ide/<rest:name>
document: /ide/index.ftd

url: /ide/<rest:name>/
document: document: /ide/with-slash.ftd

Are different, if the URL ends with /, and a pattern is defined that ends with slash (before without slash), then that will be captured, else rest will capture both urls ending with or without slash.