[MON-127] Add the api and version to the webservice URL

Append the required versioning information to the `$wgMonetizationServiceUrl`.

RFCR @saipetch @jimmordino 
If we are versioning each endpoint then having a constant for each "version" seems less useful. In other words if we have two endpoints (in the future) and they have different versions we cannot just change one constant because we could break another API call.

That was my reasoning for putting it closer to where the service method was getting invoked.