Add support for allowing request_refresh_jwt hooks with json response

[yzcheung]

Contributor Checklist
I have broken down my PR scope into the following TODO tasks

Implement request_refresh_jwt hooks
Allow JSON format responses
I have run the tests locally and they passed. (refer to testing section in contributing)

I have added tests, or extended existing tests, to cover any new features or bugs fixed in this PR

[gvwilson]

hi @yzcheung - thanks very much for your PR. We're currently trying to figure out which bits of authentication should go in dash, which should go in dash-auth, and which we should reserve for our enterprise offering - I've assigned this to myself so I don't lose track of it, and I hope to have some answers for you in a couple or three weeks. cheers - @gvwilson

[yzcheung]

hi @yzcheung - thanks very much for your PR. We're currently trying to figure out which bits of authentication should go in dash, which should go in dash-auth, and which we should reserve for our enterprise offering - I've assigned this to myself so I don't lose track of it, and I hope to have some answers for you in a couple or three weeks. cheers - @gvwilson

Cool, thanks for the update. Looking forward to hearing back soon!