Add endpoint for radiation therapy

[belkassaby]

Add endpoint that will return all children nodes of the 'radiation therapy ' maxo term : https://www.ebi.ac.uk/ols/ontologies/maxo/terms?iri=http%3A%2F%2Fpurl.obolibrary.org%2Fobo%2FMAXO_0000014&lang=en&viewMode=All&siblings=false

[BethSundberg]

@belkassaby I am confused about how the endpoint works. The link you have is to only a short list, which I don't see anywhere to choose:

But I have lots of choices for radiation therapy modality from a different ontology:

[belkassaby]

@BethSundberg it's the radiationtherapy modality. I ended up using the ncit nodes as there were more options