WeBWorK 3 backend to-do list

[drdrew42]

• [PS] refactor relationships for plural/singular relation names
• [PS] update all instances of validation to use new Validation.pm
• use ->insert wherever ->new(...) is used for row creation
• add fetch_with_defaults as an alias for discard_changes and employ everywhere add_to_$rel is used
• [PS] eliminate dependency on List::MoreUtils (firstval)
• [AP] update all $self to use more appropriate naming convention
• [GR] switch tests in t/db to use Test2::V0
• [AP] Instead of throwing errors on fields not in the DB, filter out non-existent fields. This is done in ResultSet::UserSet::addUserSet
• [PS] DeleteXXXX in ResultSet classes should return 200 OK and the tests should check to make sure that the XXX was deleted.
• resolve UserProblem problem_version (nullable with default value?) add uniqueness on user+problem+version
• Attempt field comments is a JSON column?
• Include a created_date and updated_date field in each table
• Uniformize test checking of boolean fields (and update DB to ensure proper booleans on create/update/fetch)

[drdrew42]

@pstaabp @drgrice1 feel free to add to this checklist 🙏

[pstaabp]

I just edited the list above.

[drdrew42]

discard_changes is no longer needed now that we've added retrieve_on_insert => 1 to all columns with default values. Please keep this in mind for any future DB changes that involve default values.