Implement request mapping

[edwardUL99]

Request mapping takes an inbound request into the gateway and maps it to the microservice that can handle that request. Mapping should take place as follows:

• Inbound URL: http://localhost:8080/api/gateway/microservice/items
• Mapping removes the /api/gateway/ string
• microservice is the name of the client microservice that can handle the request
• The host and port of the registered microservice is used and the remainder of the URL is passed to the microservice, so the URL becomes http://host:port/items
• The request is sent to the microservice
• The response is then sent back to the client through the gateway

Interception should take place before and after mapping

[edwardUL99]

Mostly completed, just need to test it when real microservices are linked up