🎉 Add plugable storages abstraction layer (with support for fs, s3 and db).

backend/src/app/migrations/sql/0035-add-storage-tables.sql

@@ -0,0 +1,22 @@
+CREATE TABLE storage_object (
+  id uuid PRIMARY KEY DEFAULT uuid_generate_v4(),
+
+  created_at timestamptz NOT NULL DEFAULT now(),
+  deleted_at timestamptz NULL DEFAULT NULL,
+
+  size bigint NOT NULL DEFAULT 0,
+  backend text NOT NULL,
+
+  metadata jsonb NULL DEFAULT NULL
+);
+
+CREATE TABLE storage_data (
+  id uuid PRIMARY KEY REFERENCES storage_object (id) ON DELETE CASCADE,
+  data bytea NOT NULL
+);
+
+CREATE INDEX storage_data__id__idx ON storage_data(id);
+CREATE INDEX storage_object__id__deleted_at__idx
+    ON storage_object(id, deleted_at)
+ WHERE deleted_at IS NOT null;
+