refactor messaging jobs (#19626)

Cleans up the code quality by migrating from Raw SQL to TypeORM
entities. The previous implementation was necessary to do cross‑schema
table joins but since we've migrated to the core schema we don't need it
anymore.

- Also extracted `toIsoStringOrNull` to a utility it was duplicated
several times
- Moved `isThrottled` logic from job handler to cron enqueuer

packages/twenty-server/src/utils/date/__tests__/toIsoStringOrNull.spec.ts

@@ -0,0 +1,24 @@
+import { toIsoStringOrNull } from 'src/utils/date/toIsoStringOrNull';
+
+describe('toIsoStringOrNull', () => {
+  it('should return null for null or undefined', () => {
+    expect(toIsoStringOrNull(null)).toBeNull();
+    expect(toIsoStringOrNull(undefined)).toBeNull();
+  });
+
+  it('should convert Date to ISO string', () => {
+    const date = new Date('2024-01-15T10:30:00.000Z');
+
+    expect(toIsoStringOrNull(date)).toBe('2024-01-15T10:30:00.000Z');
+  });
+
+  it('should pass through strings unchanged', () => {
+    expect(toIsoStringOrNull('2024-01-15T10:30:00.000Z')).toBe(
+      '2024-01-15T10:30:00.000Z',
+    );
+  });
+
+  it('should throw on invalid Date', () => {
+    expect(() => toIsoStringOrNull(new Date('invalid'))).toThrow(RangeError);
+  });
+});

packages/twenty-server/src/utils/date/toIsoStringOrNull.ts

@@ -0,0 +1,9 @@
+export const toIsoStringOrNull = (
+  value: string | Date | null | undefined,
+): string | null => {
+  if (value == null) {
+    return null;
+  }
+
+  return value instanceof Date ? value.toISOString() : value;
+};