Update Seqr minimiser script

[MattWellie]

Fixes

• Script which takes AIP results and minimises for Seqr doesn't 100% fit the expected API
• Based on this test data which doesn't include 'independent' as an entity, and maps on Individual ID

Proposed Changes

• Requires a Seqr mapping dictionary to convert CPG IDs to External Participant IDs
• Removes the Independent attribute from models

This is on hold pending the successful ingestion of the data generated by the script in its current form

Checklist

• Related Issue created
• Tests covering new change
• Linting checks pass

[EddieLF]

Looks good to me, once this PR is merged and released you should be able to just call the participant API endpoint for a particular project to get the ext pid to sg id dict easily.

[MattWellie]

I think this has been done in a separate branch..