[FEATURE] Create a Rest Handler to add POST _validate/detector method

[dbwiddis]

Is your feature request related to a problem?

Similar to the Rest Handler created for Create Detector or Hello World Extension or GET method in #213, create an action implementing ExtensionRestHandler with routes for the validate detector API calls handled by appropriate methods with placeholder code:

POST /detectors/_validate
POST /detectors/_validate/{type}

Java code:

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

Create a POST _validate Rest handler for validate detector similar to this. The business logic will be later done in #222.

[mloufra]

• Create RestValidateDetectorAction.java placed in AnomalyDetector repository feature/extensions branch
• Add Route method
• Add handleValidateDetectorRequest method
• Add Post_Validate action to the list of Rest Handlers in the AnomalyDetectorExtension.java

[dbwiddis]

I like the checkbox status comment!

[dbwiddis]

Completed in AD #732