This PR implements a clear-text, token-based transport protocol seen on
RV30 Plus (#937).
- Client sends `{"username": "email@example.com", "password":
md5(password)}` and gets back a token in the response
- Rest of the communications are done with POST at `/app?token=<token>`
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Co-authored-by: Steven B. <51370195+sdb9696@users.noreply.github.com>
