Creates a new constant converter.
The path to the constant representation.
The content type of the constant representation.
Input data that will be handled if it can be handled.
A promise resolving if the input can be handled, rejecting with an Error if not. Return value depends on the given type.
A RepresentationConverter that ensures a representation for a certain content type is available.
Representations of the same content type are served as is; others are replaced by a constant document.
This can for example be used to serve an index.html file, which could then interactively load another representation.