Allow tags to be modified by non-collaborators

[GCHQDeveloper36]

Problem

Tags can only be modified by collaborators, but are most useful to consumers.

Proposed Solution

Allow tags to be added by consumers to support better discovery in the marketplace and elsewhere.

Alternatives

Existing behaviour. May be worth considering whether consumers can remove tags, or just add. And/or whether new tags should be subject to approval by owners.

What is the priority of your issue?

Low

[ARADDCC002]

I think we need to consider how we implement this at an API level. If we assume that this will be done after the refactoring of model tags in #2693 then we'd need to possibly add a new end point. Currently, editing the model itself is locked down to just model owners.

[JR40159]

I'm not sure about going down the road of allowing consumers to edit properties of a model, even if it is just tags. I would expect consumers to just be able to consume data from that model.