Add "ignore path" option, to exclude path from routing

Enhancement

Currently I see no way I can exclude particular path from routing. For instance if I want my gateway to expose some endpoints.

If I have the following route configuration (/** - matches everything):

- id: frontend
  uri: ${com.siemens.cms.gateway.routes.frontend}
  predicates:
   - Path=/**

I want to be able to do something like the following (make some exclusions):

- id: frontend
  uri: ${com.siemens.cms.gateway.routes.frontend}
  redicates:
  - Path=/**, except: /actuator/**

or

spring:
  cloud:
    gateway:
      routes:
      .....
      ignore:
          predicate:
         - Path=/actuator/**

I think it would be very convenient to have such option.

Start with the Spring Cloud Gateway route configuration and the Path predicate examples in the issue. Determine how exclusions from a /** route should be represented, then verify that excluded paths such as /actuator/** are not forwarded while other paths still use the frontend route.