Add filter to allow more records in exports with tests

[tharsheblows]

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Also fixes a whitespace linting issue in an unrelated file.

Fixes #1476.

This adds a filter to set how many records are exported.

Checklist

• [ ] Project documentation has been updated to reflect the changes in this pull request, if applicable. This needs to be done in the wiki when it's released.
• [x] I have tested the changes in the local development environment (see contributing.md).
• [x] I have added phpunit tests.