Add Dataset "People" Section - Contact Point

[AlexGilleran]

• As a user cataloguing data, I want to be able to identify who should be contacted with questions/feedback around a dataset

This is part of the way to getting towards implementing this part of the form as designed:

For this issue, we just want to focus on being able to select one or more real users and setting them as contact points

Out of Scope / To be clarified later

• External contact points (e.g. for something bought from a company, you might want to put them down as the contact point)
• Displaying the contact point role (still unsure exactly how this should work)
• Any of the section under "How should the contact point(s) be referenced in the metadata" - we should just set the selected user as the contact point for now

Technical Notes

• We need a way to unambiguously set a link to the selected user rather than just setting text, probably a new aspect

[AlexGilleran]

Closing in favour of #2379