tailscale: support set device ipv4 address (#81)

* tailscale: support set device ipv4 address

https://github.com/tailscale/tailscale/blob/main/api.md#set-device-ipv4-address
Signed-off-by: Cameron Stokes <cameron@cameronstokes.com>

* add test for SetDeviceIPv4Address

Signed-off-by: Cameron Stokes <cameron@cameronstokes.com>

---------

Signed-off-by: Cameron Stokes <cameron@cameronstokes.com>

tailscale/client.go

@@ -923,6 +923,20 @@ func (c *Client) SetDeviceKey(ctx context.Context, deviceID string, key DeviceKe
 	return c.performRequest(req, nil)
 }
 
+// SetDeviceIPv4Address sets the Tailscale IPv4 address of the device.
+func (c *Client) SetDeviceIPv4Address(ctx context.Context, deviceID string, ipv4Address string) error {
+	const uriFmt = "/api/v2/device/%s/ip"
+
+	req, err := c.buildRequest(ctx, http.MethodPost, fmt.Sprintf(uriFmt, deviceID), requestBody(map[string]string{
+		"ipv4": ipv4Address,
+	}))
+	if err != nil {
+		return err
+	}
+
+	return c.performRequest(req, nil)
+}
+
 // IsNotFound returns true if the provided error implementation is an APIError with a status of 404.
 func IsNotFound(err error) bool {
 	var apiErr APIError

tailscale/client_test.go

@@ -975,6 +975,19 @@ func TestClient_SetDeviceKey(t *testing.T) {
 	assert.EqualValues(t, expected, actual)
 
 }
+func TestClient_SetDeviceIPv4Address(t *testing.T) {
+	t.Parallel()
+
+	client, server := NewTestHarness(t)
+	server.ResponseCode = http.StatusOK
+
+	const deviceID = "test"
+	address := "100.64.0.1"
+
+	assert.NoError(t, client.SetDeviceIPv4Address(context.Background(), deviceID, address))
+	assert.Equal(t, http.MethodPost, server.Method)
+	assert.EqualValues(t, "/api/v2/device/"+deviceID+"/ip", server.Path)
+}
 
 func TestErrorData(t *testing.T) {
 	t.Parallel()