Update Migration Strategy to account for all PK values

[JFriel]

Proposed Change

The current migration strategy when moving items from staging -> live only matches on the first primary key, it should match on all of the primary keys

Type of change

What types of changes does your code introduce? Tick all that apply.

• Bugfix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that would cause existing functionality to not work as expected)
• Documentation-Only Update
• Other (if none of the other choices apply)

Checklist

By opening this PR, I confirm that I have:

• Ensured that the PR branch is in sync with the target branch (i.e. it is automatically merge-able)
• Created or updated any tests if relevant
• Have validated this change against the Test Plan
• Requested a review by one of the repository maintainers
• Have written new documentation or updated existing documentation to detail any new or updated functionality and how to use it
• Have added an entry into the changelog