Approve mill certificates

Depending on your processes, you may need someone to review every mill certificate / material test report to ensure the materials meet the quality your expect. From the mill certificate detail page, or in the bulk edit view, you can now mark mill certificates as having issues or as approved.

1. Once something is approved you can no longer edit the values we store about the certificate (important for audit purposes)
2. If something was approved in error, you can unapprove it
3. You can see the approval status in the mill certificate list page and the detail page