add helper_assignments migration
update fixtures, tests accordingly
add associations
add helper_assignment model
Add fixtures, tests for helper assignments
fix associations on helper_assignment
fix iteration over all fixtures (not allowed)
rename assignments fixtures to avoid collisions, fix self-association
add tests for existent help requests, closing requests
add validation for not closing a checkin without first resolving all open issues
make checked out test more robust, verify fixture validity
add current_assignment method to help_request
add tests for help_request.current_assignment
add uniqueness check for helper checkins
add staff_6 fixtures
Add new student, unassigned assignment to fixtures
add tests for duplicate assigns to helper_assignment
refactor render_missing_params out
Add errors module
include errors module in application controller