Auth Proxy improvements

- adds the option to use ldap groups for authorization in combination with an auth proxy
- adds an option to limit where auth proxy requests come from by configure a list of ip's
- fixes a security issue, session could be reused

pkg/middleware/session.go

@@ -12,8 +12,10 @@ import (
 )
 
 const (
-	SESS_KEY_USERID = "uid"
+	SESS_KEY_USERID       = "uid"
 	SESS_KEY_OAUTH_STATE = "state"
+	SESS_KEY_APIKEY       = "apikey_id" // used for render requests with api keys
+	SESS_KEY_LASTLDAPSYNC = "last_ldap_sync"
 )
 
 var sessionManager *session.Manager