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/.sqlx/query-47130ef29ce5914528e5424fe516a9158a3ea08f8720f6df5b4902cd8094d3bb.json

@@ -0,0 +1,14 @@
+{
+  "db_name": "PostgreSQL",
+  "query": "\n        DELETE FROM shared_instance_versions\n        WHERE id = $1\n        ",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Left": [
+        "Int8"
+      ]
+    },
+    "nullable": []
+  },
+  "hash": "47130ef29ce5914528e5424fe516a9158a3ea08f8720f6df5b4902cd8094d3bb"
+}