Enketo transformer service for NEMO

Bird's eye overview

resources:

architecture/flow:

nemo talks to lib/enketo-transformer-service/index.js (separate node app that runs enketo-transformer) to convert our form XML into a JSON object we're able to send to enketo
nemo renders a <div id="enketo"> in enketo_form.html.erb
nemo injects 2 variables into JS via a <script> tag:
- window.ENKETO_MODEL_STR is the form XML from enketo-transformer-service
- window.ENKETO_INSTANCE_STR is the optional response XML (when editing)
enketo injects itself into document.querySelector('#enketo form') via jQuery in packs/enketo.js
enketo loads the two variables set above and renders the form
user types in info and hits submit
enketo submits XML to nemo's existing ODK /submission (responses#create) route
on edit, nemo saves the edited XML to modified_odk_xml attachment so as to preserve the original odk_xml as required by some orgs

If you get errors trying to yarn install:

Make sure you are using the correct node version: the one specified in ../../.nvmrc
Try explicitly specifying the C++ compiler used by Enketo dependencies: yarn install -std=c++17