Clean up style
Fix references in class summaries
Combine Where+FirstOrDefault queries
Break up large method, long lines
Add validation on file extension
Apply test naming conventions
Extract mock of Movie class, comment on why not mocking interface
Co-authored-by: Cody Robibero <cody@robibe.ro>
Co-authored-by: Claus Vium <cvium@users.noreply.github.com>
