Merging collections and the /tpf endpoint

[joepio]

Collections and the /tpf endpoint have some similarities. Both allow for filtering all triples by property / value. However, collections are more powerful, as they also enable pagination and sorting.

The /tpf endpoint currently uses a lot of custom logic, which might not be needed anymore if we switch to using collections.

Also, the subject field in TPF is not really useful in Atomic data, except when you want to find an Atom by subject and value.

[joepio]

Perhaps use the standardized query params / Atomic Endpoints for this: atomicdata-dev/atomic-data-docs#15

[joepio]

Another important difference between TPF endpoints and Collections is that Collections return Subjects, while TPF queries typically return Atoms (triples).

[joepio]

Done!