//   matches /foo/bar/baz, but does not match /foo/barbaz).
  // * ImplementationSpecific: Interpretation of the Path matching is up to
  //   the IngressClass. Implementations can treat this as a separate PathType
  //   or treat it identically to Prefix or Exact path types.
  // Implementations are required to support all path types.
  // Defaults to ImplementationSpecific.
  optional string pathType = 3;

  //   matches /foo/bar/baz, but does not match /foo/barbaz).
  // * ImplementationSpecific: Interpretation of the Path matching is up to
  //   the IngressClass. Implementations can treat this as a separate PathType
  //   or treat it identically to Prefix or Exact path types.
  // Implementations are required to support all path types.
  // Defaults to ImplementationSpecific.
  optional string pathType = 3;

  //   request path. Note that if the last element of the path is a substring
  //   of the last element in request path, it is not a match (e.g. /foo/bar
  //   matches /foo/bar/baz, but does not match /foo/barbaz).
  // * ImplementationSpecific: Interpretation of the Path matching is up to
  //   the IngressClass. Implementations can treat this as a separate PathType
  //   or treat it identically to Prefix or Exact path types.

In Kubernetes 1.18, there are two significant additions to Ingress: A new `pathType` field and a new `IngressClass` resource. The `pathType` field allows specifying how paths should be matched. In addition to the default `ImplementationSpecific` type, there are new `Exact` and `Prefix` path types. 

  - `servicePort` -> `service.port.name` (for string values)
  - `servicePort` -> `service.port.number` (for numeric values)
  - `pathType` no longer has a default value in v1; "Exact", "Prefix", or "ImplementationSpecific" must be specified

  Other Ingress API updates:
  - backends can now be resource or service backends