Add state to track explicitly whether files match

Checklist

[x] Add description
[x] Reference the open issue that the pull request addresses
[x] Pass code quality checks
- spin up docker docker-compose up -d --build
- enter api container docker-compose exec api /bin/bash
- run api tests make validate
- exit container ctrl/command+D or exit
- enter web container docker-compose exec web /bin/sh
- run front-end tests npm run test or npx jest
- lint npm run lint-fix
- exit container as above
[x] Request code review
- Please allow 36 hours from opening a pull request before merging a pull request- even if it has already received an approving review.
[x] Address comments on code and resolve requested changes
[x] Merge own code

Issue: #460

Brief description of solution

Find the bug: there was an effect that opened the confirmation page only if there was no error message, but the effect was triggered before the error message could be set
Create a new state to track explicitly whether the files match, and use that state to determine whether to open the confirmation page
Fix a failing test