Endpoint to get the allow web admin properties on the Addon manager module.

Create an endpoint that returns a read-only value of module.allow_web_admin the value so as to disable start modules if its set to false.
Currently, there is no way to get the value of module .allow_web_admin using a rest endpoint, 

this ticket seeks to create an endpoint to get the read-only value.
The endpoint is to be used on the Add-on manager so as to restrict admin priviledges if it is set to false.