This is the first part of a larger migration to convert Zulip's
reactions storage to something based on the codepoint, not the emoji
name that the user typed in, so that we don't need to worry about
changes in the names we're using breaking the emoji storage.
A deactivated realm emoji should neither be accepted further as a
reaction nor its further occurences in a message be rendered as an
emoji. However, all the old occurences should continue to render
normally.
- Add file_name field to `RealmEmoji` model and migration.
- Add emoji upload supporting to Upload backends.
- Add uploaded file processing to emoji views.
- Use emoji source url as based for display url.
- Change emoji form for image uploading.
- Fix back-end tests.
- Fix front-end tests.
- Add tests for emoji uploading.
Fixes#1134
Use `name_to_codepoint.json` file (and the similar structure in
emoji_codes.js) to map emoji names directly to codepoints and change
the rendered emoji image to `unicode/<codepoint.png>` rather than
`<emoji_name>.png`.
Fixes: #3539.
Tim Abbott
Harshit Bansal
Cory Lynch
K.Kanakhin