carddav: add very basic Client

client.go

@@ -28,7 +28,7 @@ func (c *Client) FindCurrentUserPrincipal() (string, error) {
 		return "", err
 	}
 
-	var prop currentUserPrincipalProp
+	var prop currentUserPrincipal
 	if err := resp.DecodeProp(name, &prop); err != nil {
 		return "", err
 	}