Apply CORS headers to a specific request. This is useful if you only have a single action that needs CORS headers, and you don't want to pay for conditional checks on every request.
You should note that applyCORS needs to be used before you add any method combinators. For example, the following won't do what you want:
method POST $ applyCORS defaultOptions $ myHandlerThis fails to work as CORS requires an OPTIONS request in the preflighting
stage, but this would get filtered out. Instead, use
applyCORS defaultOptions $ method POST $ myHandler