Initial shared instances backend (#3800)

* Create base shared instance migration and initial routes

* Fix build

* Add version uploads

* Add permissions field for shared instance users

* Actually use permissions field

* Add "public" flag to shared instances that allow GETing them without authorization

* Add the ability to get and list shared instance versions

* Add the ability to delete shared instance versions

* Fix build after merge

* Secured file hosting (#3784)

* Remove Backblaze-specific file-hosting backend

* Added S3_USES_PATH_STYLE_BUCKETS

* Remove unused file_id parameter from delete_file_version

* Add support for separate public and private buckets in labrinth::file_hosting

* Rename delete_file_version to delete_file

* Add (untested) get_url_for_private_file

* Remove url field from shared instance routes

* Remove url field from shared instance routes

* Use private bucket for shared instance versions

* Make S3 environment variables fully separate between public and private buckets

* Change file host expiry for shared instances to 180 seconds

* Fix lint

* Merge shared instance migrations into a single migration

* Replace shared instance owners with Ghost instead of deleting the instance

apps/labrinth/src/database/models/user_item.rs

@@ -511,6 +511,18 @@ impl DBUser {
             .execute(&mut **transaction)
             .await?;
 
+            sqlx::query!(
+                "
+                UPDATE shared_instances
+                SET owner_id = $1
+                WHERE owner_id = $2
+                ",
+                deleted_user as DBUserId,
+                id as DBUserId,
+            )
+            .execute(&mut **transaction)
+            .await?;
+
             use futures::TryStreamExt;
             let notifications: Vec<i64> = sqlx::query!(
                 "