Validate sponsor inactivation

JIRA https://osraav.atlassian.net/browse/OSRA-184

- implement validation that checks whether sponsor has active sponsorships before allowing its status to be changed from 'Active' to any other
- create new seeding_steps.rb that can be filled out with other reference objects and used throughout the Cucumber suite

OSRA-184 #Code-Review
these unless statements feel like a code smell we need to address