326 remove "products" from exposed classes

[alexdunnjpl]

🗒️ Summary

Per @tloubrieu-jpl in #326, "products" is confusing when overloaded to describe "products which are not aggregate products.

This PR removes 'products' from the results returned by endpoint /classes, and removes it as a enumerated class value for endpoint /classes/{class}.

It also performs significant renaming of related concepts within the API, specifically:

Relevant Product-prefixed classes classes are now named with NonAggegateProduct prefix instead.
GroupConstraint methods any(), all() and not() have been renamed to filter(), must() and mustNot(). These new names directly reflect the search concepts they conceptually map to, and should avoid confusion in future.

A method union() is implemented for GroupConstraint and later reverted. I haven't written unit tests for it and can't be bothered since it ended up not being required, but it's left in the commit history just in case a use-case for it comes up in future.

⚙️ Test Data and/or Report

Postman tests pass. Postman tests written and PR will be opened to add them to the registry repo's tests

♻️ Related Issues

fixes #326

[alexdunnjpl]

Oh, and I deleted the obsolete/non-maintained postman tests file and replaced it with a readme so devs can find the real one.