Processes message, adding all the necessary extra headers and parameters to ensure that it's correctly authenticated and
authorized under the given domain for the online service.
Basically, if a query is not processed by calling this method on it, it will be sent to the online service as if it's a query from a
non-logged-in user. Similarly, if the Authorizer isn't authenticated or authorized (
for domain), no changes will be made to the message.
domain may be null if the request doesn't require authorization.
This modifies message in place.
This method is thread safe.
| this | |
| domain |
the AuthorizationDomain the query falls under, or null |
| message |
the query to process |