create Dispatcher#getAll(key)

[terrablue]

Dispatchers can often facade a multitude of values per key.

A Dispatcher#getAll(key: string): string[] function would return all values associated with a key.

• query: /?a[0]=b0&a[1]=b1
• path: routes/my-repo/[...subpath].js
• cookies: ?
• headers: Headers can contain multiple values. The WHATWG implementation of #get() returns them concatenated with a comma, which is generally inconsistent with URLSearchParams#getAll and FormData#getAll.

Would it make sense to create typed versions of getAll, like those of get, that operate on every member of the array? For example, for a given type uuid that verifies a string is a UUID, create a getAllUuid function on request.{query,path,cookies,headers} that evaluates all members of the property.