Do not store data as encoded string but as data URL.
Set a default mime type for text attachment if not provided.

Allow to choose which action_reference will be used as default view.

openCursor only return one entry per index value by default.
Use IDBKeyRange to get the expected behaviour.

Simplify storage and tests code.

Change the database structure so that the "attachment" store contains one entry per attachment.

Add tests for memorystorage.
Drop copy/paste code in jio.post. Should be added in a standalone storage if needed.

All ERP5 callable can be represented as attachment.
Editing (FormData) is done with putAttachment.

It is not possible to directly create/modify.

Contrary to previous implementation, the content is not shared between all memory storages.

Allow to read all entries in localStorage.
localStorage becomes just one jio document with many attachments.