Fix 284 by adding AlternateDownloader to handle Safari's nonsense

[shaunanoordin]

Fixes #284

What?

• When a user (using Safari) attempts to download a CSV, she/he will properly receive a 'Save As' dialog (or saved immediately, depending on user settings) for a .CSV file... as expected.
• Currently this only works with the Map Explorer's Download feature; a solution for Students>Assignments is in progress.

How?

• Since Safari doesn't like SaveAs, <a href="..." download> or any app-level solution for forcing a Save As dialog to open, the AlternateDownloader sends the data to the EduAPI, which then echoes the data back as a server response full of content-disposition: download this goddamn thing as a file headers.
• This requires a hidden <form> that triggers the "old-fashioned" HTTP request that Safari needs.
• Much thanks to @marten for the EduAPI download echo service ( zooniverse/education-api#30 ) that this relies on and to @astopy for increasing the EduAPI's upload limit.

WARNING: it may be conceivable that, in the future, the amount of data that a user can query will grow even larger, exceeding the already generous upload limit, so we need to consider preemptively curbing the download size at the app level. Right now, the largest CSV file that can get echoed (uploaded-then-downloaded-again) is about 12MB in size, if the user requests for all aggregated results. I'm looking into zipping the content to reduce strain on the EduAPI.

@simoneduca, please feel free to review and comment on this, as I'm thinking of generalising the CSV download function into a component that can be used by Students>Assignments, not just Map Explorer.

@ali I just realised how ironic it is that it's so difficult to get a Safari going in Gorongosa.

[shaunanoordin]

Just to clarify the New Plan:

• I'm creating the SuperDownloadButton component that handles all CartoDB-download functions.
• Once functional (i.e. it stops bugging out on me), I'll slot it into Students > Assignments
• This will also implement the CSV "EASYMODE" header translations to Students > Assignments, and will fix #276 and address " update csv headers for data downloaded on assignments page" in #278.

I'm taking a break from the zipping functionality for the moment; I may need to simply limit all downloads to 10000 items like before for the time being, while I figure out wtf is up with the file formats I'm getting back.

The individual functions are working fine, but since they tend to be rather interlocked in the supercomponents they exist in, I'm still trying to find an elegant way to package all those functions into a standalone SuperDownloadButton component.

[shaunanoordin]

• The "Download from CartoDB" functionality that was spread across Map Explorer and Students Assignment have been consolidated into a single SuperDownloadButton component.
• EASYMODE is built in, but has not been enabled for Student Assignments yet - I'm still looking at the best CSV format for those CSVs

[shaunanoordin]

• EASYMODE enabled! Download buttons on Map Explorer and Student Assignments now provide a CSV that's somewhat more readable to humans... and are all standardised to one format, to boot.
• I'll need to test this with live data (zootester1 on production after doing a few Classifications on an Assignment) to know for sure, but...
  • ...I suspect I may need to get another PR to tweak the difference between percentage_behaviour (aggregated results) and what_i_marked_as_behaviour (My Classifications) values.

New look

@simoneduca, this is ready for review when we're back next week! Woot!

[simoneduca]

On my screen

I'd recommend setting max-width: 75em in .student-assignmentlist

[simoneduca]

Please add readOnly to the input fields in the form of SuperDownloadButton to suppress react warning Warning: Failed form propType: You provided avalueprop to a form field without anonChangehandler. This will render a read-only field. If the field should be mutable usedefaultValue. Otherwise, set eitheronChangeorreadOnly. Check the render method ofSuperDownloadButton.

[shaunanoordin]

Update:

• aria-xxx and readOnly tags added to SuperDownloadButton to take care of errors.
• Action Buttons in Student Assignment List rearranged to stack vertically, to better support content when Assignments have long descriptions.

👍 Thanks for the feedback, @simoneduca!

[simoneduca]

LGTM 👍