Attachments uploaded by reporters have no created_by value

[4c0n]

Description

The current data migration logic is incorrect. I assumed that the created_by value would be the email address of the reporters, but it turns out that is not the case.

Checklist

• Keep the PR, and the amount of commits to a minimum
• The commit messages are meaningful and descriptive
• The change/fix is well documented, particularly in hard-to-understand areas of the code / unit tests
• Are there any breaking changes in the code, if so are they discussed and did the team agreed to these changes
• Check that the branch is based on main and is up to date with main
• Check that the PR targets main
• There are no merge conflicts and no conflicting Django migrations