View Provider: Selection of identifier should be improved

[dirk-ecker]

At this time I use all possible identifiers to search for the input given by the user, but that makes no sense. It should be only identifiers that belongs to providers, I think.

So we need a way to search for identifiers of a given entity by adding a new parameter for the rest endpoint identifiers - entity as string - or, I think the better alternative, support a method to find identifiers in the context of the entity i.e. /rest/providers/identifiers.

In contrast to /rest/providers/42/identifiers the request to /rest/providers/identifiers addresses all identifiers that belongs to providers.

[hornmo]

I don't think I fully understand this one. Can you specify possible request parameters as well as an example of a result payload you would expect?