Remove create dtxsid by api

[dannypeterson]

Removes the ability to create DSSTox model through Epi Exposure API, as validation does not properly pull data. create method was added to DSSTox viewset which properly populates ccte content correctly for dtxisd. Modified and created tests.

[shapiromatron]

Looks good. I think you need to fix your vscode so it stops adding trailing commas; its hard to review b/c there are a bunch of unintended formatting changes.

I think we need a test where the dtxsid is invalid, like dtxsid0000000000 or something like that?

[shapiromatron]

LGTM - I made a few edits including a permissions change, but nothing major other than that - nice job!

• 273dfca split tests
• 9f10b6c make relative import when working in app
• b807e65 minor code refactor
• 5667497 require login for creation