Compiling a URLPattern component will generate a 'parts list' which
is used for generating the regular expression that is used for
matching against URLs.
This parts list is also used to generate (through this function) a
pattern string. The pattern string of a URL component is what is
exposed on the USVString getters of the URLPattern class itself.
As an example, the following:
```
let pattern = new URLPattern({ "pathname": "/foo/(.*)*" });
console.log(pattern.pathname);
```
Will log the pattern string of: '/foo/**'.
These control how a pattern string is generated, which can vary for
different components and is also impacted by the 'ignoreCase' option
that can be provided in the URLPattern constructor.
This is to save a future name conflict that will appear between
the options IDL dictionary and the options struct that are both
present in the spec.
It is also a nicer interface for now given there is only a single
option at the moment.
As the comment in this file explains the caller of LibURL APIs are
meant to assume if they see any error, that it is a TypeError since
that is all the spec throws at the moment.
A custom error type exists here so that we can include more
information in TypeError's which are thrown.
This is the core object behind a URL pattern which when constructed
can be used for matching the pattern against URLs.
However, the implementation here is missing key functions such as
the constructor and the 'test'/'exec' functions as that relies on
a significant amount of supporting URLPattern infrastructure such
as two different parsers and a tokenizer.
However, this is enough for us to implement some more of the IDL
wrapper layer of this specification.
A URL pattern consists of components such as the 'port', 'password'
'hostname', etc. A component is compiled from the input to the
URLPattern constructor and is what is used for matching against
URLs to produce a match result.
This is also where the regex dependency is introduced into LibURL
to support the URLPattern implementation.
This is the return value of a URLPattern after `exec` is called on it.
It conveys information about the named (or unammed) regex groups
matched for each component of the URL. For example,
```
let p = new URLPattern({ hostname: "{:subdomain.}*example.com" });
const result = pattern.exec({ hostname: "foo.bar.example.com" });
console.log(result.hostname.groups.subdomain);
```
Will log 'foo.bar'.
The URLPattern spec is intended to be implemented inside of LibURL, with
LibWeb only responsible for the IDL conversion layer, in a similar
manner to how URL is implemented.
