A map of context items for the request.

This is especially useful for passing application specific data down the chain of processors along with the request itself.

For example, a generic route may be defined to check user login status, if the user is logged in, add a reference to user specific data to the context.

This is implemented with std.variant.Variant to allow any type of data.

class HTTPServerRequest
DictionaryList!(Variant, true, 2) context;