Handle new error codes from the media upload endpoint

[maxme]

Expected behavior

In case of an error during media upload, we should show the exact error to help the user take a decision.

The list of errors are defined here in Calypso. Most interesting are:

• rest_upload_limited_space
• rest_upload_file_too_big
• rest_upload_user_quota_exceeded

Note that these error codes are actually stored in the message field. Here is an sample response we get from the https://public-api.wordpress.com/rest/v1.1/sites/{SITE_ID}/media/new/ API endpoint in case of an upload on a quota limited site:

{
    "error": "upload_error",
    "message": "rest_upload_user_quota_exceeded|You have used your space quota. Please delete files before uploading. Back"
}

• On the network side: It would be a good idea to split the error message (something like .split("|")), make the error code directly accessible by the UI.
• On the UI, we should handle that error and display the message correctly instead of showing a generic message. This must be done:
  • In the media library.
  • In the editor.

Actual behavior

We show a generic error in the editor and in the media library:

Media Library	Editor

More details on paaHJt-17e-p2

WPAndroid related ticket: https://github.com/wordpress-mobile/WordPress-Android/issues/12325

[designsimply]

This came up in an app review:

For a very brief period, I was able to upload photos. But you broke it again in one of the recent updates. I honestly don’t do much worth WordPress except make blog posts with pics. But now pics won’t upload.

Suggestion: Provide more detailed error messages when uploads fail.

^{1-star app review by Jentropy – Aug 12, 2020 | WPiOS 15.3}

^{(internal reference: app-store-reviewId=6311920580)}