Add default role to workspace (#10444)

## Context
Adding a defaultRole to each workspace, this role will be automatically
added when a member joins a workspace via invite link or public link
(seeds work differently though).
Took the occasion to refactor a bit the frontend components, splitting
them in smaller components for more readability.

## Test
<img width="948" alt="Screenshot 2025-02-24 at 14 54 02"
src="https://github.com/user-attachments/assets/13ef1452-d3c9-4385-940c-2ced0f0b05ef"
/>

packages/twenty-front/src/pages/settings/roles/components/RolesTableHeader.tsx

@@ -0,0 +1,25 @@
+import { Table } from '@/ui/layout/table/components/Table';
+import { TableHeader } from '@/ui/layout/table/components/TableHeader';
+import { TableRow } from '@/ui/layout/table/components/TableRow';
+import styled from '@emotion/styled';
+import { Trans } from '@lingui/react/macro';
+
+const StyledTableHeaderRow = styled(Table)`
+  margin-bottom: ${({ theme }) => theme.spacing(2)};
+`;
+
+export const RolesTableHeader = () => {
+  return (
+    <StyledTableHeaderRow>
+      <TableRow>
+        <TableHeader>
+          <Trans>Name</Trans>
+        </TableHeader>
+        <TableHeader align={'right'}>
+          <Trans>Assigned to</Trans>
+        </TableHeader>
+        <TableHeader align={'right'}></TableHeader>
+      </TableRow>
+    </StyledTableHeaderRow>
+  );
+};