Batch import of facilities from CSV

[anibalsolon]

Import a CSV file containing one facility per line, that matches a provided template.

The interface flow should be:

1. A drop place or a file selector, to upload the file (using e.g. https://github.com/react-dropzone/react-dropzone)
2. Load and parse CSV using the HMTL5 File API: https://developer.mozilla.org/en-US/docs/Web/API/File/Using_files_from_web_applications
3. Check if it matches with the template
4. Check for invalid values (e.g. GPS position out of range)
5. Provide a data table for user checking
6. For each table line, execute the addFacility mutation, storing the response to show the user
7. Show progress bar

[anibalsolon]

About item #6 :

Since the mutation addFacility will be executed 20x for a CSV with 20 lines, it should be better to group them into one single HTTP request, instead of 20 requests.

To address this scenario, Apollo provides a batcher, that will group operations executed quasi-simultaneously. It groups operations in a default range of 10ms. It can be changed using the batchInterval option.

https://www.apollographql.com/docs/link/links/batch-http.html