Is your feature request related to a problem?

Similar to the Rest Handler created for Create Detector or Hello World Extension, create an action implementing ExtensionRestHandler with routes for the get detector API calls handled by appropriate methods with placeholder code:

GET detectors/{detectorId}
GET detectors/{detectorId}?job=true

Java code:

private ExtensionRestResponse handleGetRequest(ExtensionRestRequest request) {
    // do things with request
    return new ExtensionRestResponse(request, OK, "placeholder");
}}

Create a GET Rest handler for get detector similar to this. The business logic will be later done in #214