feat: adds a reference back to Subject from Sample

[claymcleod]

PR Close Date: November 17, 2023

Adds a reference back to the Subject from which a Sample was derived.

Considerations

• I made this a required field, I'm not if it will hold true for all servers that every sample can be tied back to a subject reported on by that server. I do know it's true for us FWIW.
• I considered a few other names, including parent, derived_from, and source, but ancestor seemed like the best choice. Let me know if anyone likes a different name better.

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[e-t-k]

What about simply subject ? Would that be too confusing? (Or other technical reasons to avoid it?) I agree that ancestor is better than parent etc.

The Treehouse server will always report on a Subject for each Sample we serve, even if that Subject isn't originally ours (eg TARGET/ other 3rd party samples on which we've calculated gene expression); so that constraint will be fine for us as well.

LGTM in general though.

[claymcleod]

Great! Thanks for your comments. I do slightly like subject better, so I will update that and see what other commenters think.

[claymcleod]

Note to self: I will need to update this to use the new models::subject::Identifier when #27 is merged in.