Move RealClientIP code to IP packages

pkg/apis/ip/interfaces.go

@@ -0,0 +1,11 @@
+package ip
+
+import (
+	"net"
+	"net/http"
+)
+
+// RealClientIPParser is an interface for a getting the client's real IP to be used for logging.
+type RealClientIPParser interface {
+	GetRealClientIP(http.Header) (net.IP, error)
+}