Attempt to Address Issue-225 and Issue-226.

[markpbaggett]

What Does This Do?

This makes MakeCollection create a Collection when there are items or a CollectionRef when there are not. It also pops items on data for MakeManifest so that we don't accidentally end up with an embedded Manifest. This is needed due to an issue with Reference and extra.allow.

[glenrobson]

We should update the description to mention if you don't pass in items then it creates a CollectionRef.

How easy is it to convert a CollectionRef to Collection? If a user doesn't pass items then tries to add it later will this cause an error? Should we have two methods, make_collection and make_collection_ref to make it more explicit?

[markpbaggett]

@glenrobson, you are right. If this comes in and someone did this:

j = collection.make_collection(
    id="https://example.com/collection/2",
    label="No props with items",
)
j.make_manifest(
    id="https://example.com/collection/2",
)
print(j)

You're going to get an error since make_manifest() doesn't exist on CollectionRef. Let's go with your idea for two different helpers.