Messagebus Probe WebHook should respond with WWW-Authenticate entry in header for authentication

As defined here: https://developer.mozilla.org/en-US/docs/Web/HTTP/Authentication :

"RFC 7235 defines the HTTP authentication framework, which can be used by a server to challenge a client request, and by a client to provide authentication information.

The challenge and response flow works like this:

1. The server responds to a client with a 401 (Unauthorized) response status and provides information on how to authorize with a WWW-Authenticate response header containing at least one challenge.

2. A client that wants to authenticate itself with the server can then do so by including an Authorization request header with the credentials.

3. Usually a client will present a password prompt to the user and will then issue the request including the correct Authorization header."

So, when implementing a workflow that interacts with MessageBus Probe WebHook, because the probe is acting as a server, one would expect to receive the challenge (WWW-Authenticate entry in header) in the response. For more details about the response headers expected to define the authentication method are described in that document, in section "WWW-Authenticate and Proxy-Authenticate headers"

In our case, we are interested in the WWW-Authenticate header, more specifically with = Basic. It would be nice to be able to configure the value for realm via the properties file, but that is not really required. Currently, we are receiving the 401 response, but we are missing the WWW-Authenticate response header from step 1 above. Because we do not have that header entry, the flow of the authentication is broken and we cannot move to Step 2.