feat(backend): start on fediverse auth support

scripts/migrate/009_fediverse_oauth.sql

@@ -0,0 +1,15 @@
+-- +migrate Up
+
+-- 2023-03-16: Add fediverse (Mastodon/Pleroma/Misskey) OAuth
+
+create table fediverse_apps (
+    id            serial primary key,
+    instance      text not null unique,
+    client_id     text not null,
+    client_secret text not null,
+    instance_type text not null
+);
+
+alter table users add column fediverse text null;
+alter table users add column fediverse_username text null;
+alter table users add column fediverse_app_id integer null references fediverse_apps (id) on delete set null;