Validate against and attempt fixing of incorrectly formatted HTML5 ZIPs

[bjester]

Background

Kolibri's HTML5 ZIPs need to be formatted a certain way, with an index.html file at the root of the ZIP, in order to render it. This can cause confusion for users who use consumer tools to create a ZIP file, which usually adds a parent directory within the ZIP.

Desired behavior

• Studio should validate that the ZIP file is formatted correctly with an index.html file at the root of the ZIP at upload
• If there isn't an index.html file at the root of the ZIP, but there is a single folder at the root which does, we should attempt to fix it by unzipping and re-zipping it
• Otherwise, it should make the node incomplete when the file isn't correct and show the appropriate feedback to the user regarding the issue.

Current behavior

No validation exists, but the preview does mention that it is missing the index.html

Value add

Validation at time of upload will avoid headaches for users who go through the process of curating content, publishing a channel, importing it into Kolibri, only to find that the file doesn't work.
https://community.learningequality.org/t/kolibre-index-for-html/2783