Expose a CSV API endpoint of our aggregated drawings data to use with the HXL Proxy

[krissy]

Semi-blocked by: #146, #145
Relates to: #160

What

We are integrating with the Humanitarian Data Exchange (HDX) - see the project/milestone description for background.

As a first step, we want to expose a public .csv endpoint holding data that conveys the "Number of displaced children and their conveyed moods in art therapy".

This will display HXL-formatted content using the database view we created in #145. Once this endpoint is ready, we can use it as a source to create a new HXL Proxy API, which will serve a JSON endpoint for our data visualization graphs to use going forward.

Please refer to the data in #146 for what to replicate. You can also check out the ticket details in #160 to see how this will eventually be used for context.

NB: Though this is blocked by completion of #146, you can already get a start on setting up the new route and CORS fix specified below.

How

• New endpoint: Refer to this spike PR which currently exposes a HXL-formatted CSV when you access the URL /drawings.csv. Now that the HXL data design doesn't correspond to the drawings#index action, we want to decouple this with the index route and replace this with a separate endpoint that makes sense. E.g. /hdx_report_drawings.csv.
• Make it (and only it) public. For some reason CORS (cross-origin resource sharing) isn't enabled despite this commit from the original hackathon, and you still have to be logged in to access any of these internal endpoints. This is a "good bug" at the end of the day, because we don't want to expose the drawings until we confirm which drawings we have the consent to expose the data for. However, this particular CSV endpoint CAN be exposed publicly because it's just overall totals and nothing to do with personal information. The ideal task for this is to ensure CORS is disabled for all other endpoints except this one.

Output and Test

• Share all the endpoint and response details in your resulting PR
• Feed this endpoint into a test HXL API Proxy instance https://proxy.hxlstandard.org/data/source, and share the results with the team