Easier to see who belongs together in the plan board

Within a project, several pairs of employees are running. This is difficult to see through the planning board. The pairs are mixed up and can only be distinguished by an icon, and sometimes the color of the icon is also very similar.

The goal is to easily see which employees belong together.
- With a colored line around the receipts (useful in resource employees)
- Group employees (useful in resource projects)
- Highlighting group when you hover over it (same idea as ctrl click)