Update App Gateway with Indendent Network and Add WAF/Firewall Protections

[marycrawford]

As DevOps Engineers, we would like to implement a (1) firewall and (2) separate networking for our Azure App Gateway to further secure our web application and APIs.

• Added Benefit and Value: The Web Application Firewall (WAF) will help engineers automate the protection of our application from common web vulnerabilities and attacks by monitoring and filtering HTTP traffic to and from your application. In addition, the separate subnet where the Application Gateway is deployed must be free of any other resources to avoid conflicts with other subnets.