Revisit Consortia Picker

[feserm]

The "Consortia picker" in the service registration form feels a little unintuitive. Maybe a could be an alternative?

[feserm]

It was a deliberate choice to not use a select mutliple. The implementation follows a common practice of having two lists with control buttons (multiple select list).
I will see, if I can revisit the component and tweak the functionality a bit, but in general the component will stay the same