Add filter to and field selection to /samples

[awm33]

In response to the needs presented in cognoma/cancer-data#29 we need to add the ability for the frontend to get a list of samples related to a given mutated gene.

Example:
/samples?mutations__gene=1234&mutations__status=true&&fields=sample_id

Looks like the SearchFilter class supports filtering related models. The dynamic fields library can be used to filter fields. Note: Even though the examples use ModelSerializer, it should work with the regular Serializer used in this repo.

[dhimmel]

Would it be possible to specify a list of genes as well and for each gene receive a list of samples with that mutation?

I can imagine many situations where the frontend will need the samples with a mutation for multiple mutations and it would make sense to just do one network query.

[awm33]

@dhimmel The endpoint returns sample objects with mutations being a child. I think what you're describing might be achieved through /samples?mutations__gene=1234&mutations__gene=2356&mutations__gene=21883&fields=sample_id,mutations

Maybe adding mutations as a searchable relation on /genes may make sense as well. For example /genes? entrezid=90808&entrezid=89979&entrezid=8668&mutations__status=true&expand=mutation&fields=entrezid

Then gene.mutations[...].sample would have the sample ids.

I just used 3 as an example, idk how many genes would be typical.