[0.19.0] - Account backup option

[mormaer]

Introduction

As detailed in the recent Lemmy announcement from version 0.19.0 users will have the option to export and import a backup of their profile information.

Users can now export their profile settings data (including subscriptions and blocklists) via GET /api/v3/user/export. The returned JSON data should not be parsed by clients, but directly downloaded as a file. Backups can be imported via POST /api/v3/user/import.

https://github.com/LemmyNet/lemmy/pull/3976

Requirements

We should look to add support for this ASAP, it will need to be gated behind a version check as it is not supported on earlier versions.