Create typeguards for widget configurations (#16627)

We checked for widget types by doing `configuration?.__typename ===
'LineChartConfiguration'` which made the code difficult to read.

In this PR, I introduce type guards for each widget type.

Note: the configuration type is `WidgetConfiguration |
FieldsConfiguration` for now but should be changed to
`WidgetConfiguration` when @Devessier adds FieldsConfiguration to the
backend type `WidgetConfiguration`.

packages/twenty-front/src/modules/command-menu/pages/page-layout/utils/isLineChartConfiguration.ts

@@ -0,0 +1,11 @@
+import { type FieldsConfiguration } from '@/page-layout/types/FieldsConfiguration';
+import {
+  type LineChartConfiguration,
+  type WidgetConfiguration,
+} from '~/generated/graphql';
+
+export const isLineChartConfiguration = (
+  configuration: WidgetConfiguration | FieldsConfiguration | null | undefined,
+): configuration is LineChartConfiguration => {
+  return configuration?.__typename === 'LineChartConfiguration';
+};