Make a Mock of this server for testing with Docassemble

[BryceStevenWilley]

While we do also want to mock Tyler's servers (see #287), it would also help to have a separate level mock for this server, for testing
docassemble interviews (i.e. specifically for testing with certain case results, which would be possible with a Tyler mock, but much more difficult).

Some resources:

• https://stackoverflow.com/questions/38344711/swagger-openapi-mock-server
• https://docs.imposter.sh/rest_plugin/
• https://github.com/stoicflame/enunciate-openapi