Remove AuthToken method

The method is only used in the rpc client constructor

rpc/client.go

@@ -130,7 +130,9 @@ func NewRpcClient(trans transport.Requester) (RpcClientApi, error) {
 	c.routineTracker.Add(1)
 	go c.subscribeToNotifications(ctx, notificationChan)
 
-	c.authToken, err = c.AuthToken()
+	authToken, err := WaitForRequestNoAuth[serde.NoPayloadRequest, string](c, serde.GetAuthTokenMethod, serde.NoPayloadRequest{})
+	c.authToken = authToken
+
 	return c, err
 }
 
@@ -148,14 +150,6 @@ func (rc *rpcClient) Address() (common.Address, error) {
 	return rc.nodeAddress, nil
 }
 
-// AuthToken fetches an authentication token from the nitro node
-func (rc *rpcClient) AuthToken() (string, error) {
-	if rc.authToken == "" {
-		return WaitForRequestNoAuth[serde.NoPayloadRequest, string](rc, serde.GetAuthTokenMethod, serde.NoPayloadRequest{})
-	}
-	return rc.authToken, nil
-}
-
 // CreateVoucher creates a voucher for the given channelId and amount and returns it.
 // It is the responsibility of the caller to send the voucher to the payee.
 func (rc *rpcClient) CreateVoucher(chId types.Destination, amount uint64) (payments.Voucher, error) {