Magnets: one power supply controlling several multipoles #478

Description, motivation and use case
Combined function magnets connected in series. It's one power supply controlling, for example, both quadrupole and sextupole component of several magnets.

Proposed solution
...

Describe alternatives you've considered
...

Example
...

Additional context
...

Checklist

• I've assigned this issue to a project
• I've @-mentioned relevant people @TeresiaOlsson