feat: store whether registration is open

db/migrations/00005_site_registration.sql

@@ -0,0 +1,5 @@
+-- +goose Up
+-- site 表没有行或者 brand_name 为 NULL 时，品牌名是默认的 Alisten；没有行时开放注册。
+ALTER TABLE site
+    ALTER COLUMN brand_name DROP NOT NULL,
+    ADD COLUMN registration_open boolean NOT NULL DEFAULT true;

db/queries/site.sql

@@ -1,6 +1,10 @@
--- name: BrandName :one
-SELECT brand_name FROM site;
+-- name: SiteSettings :one
+SELECT brand_name, registration_open FROM site;
 
 -- name: SetBrandName :exec
 INSERT INTO site (brand_name) VALUES (@brand_name)
 ON CONFLICT (id) DO UPDATE SET brand_name = excluded.brand_name;
+
+-- name: SetRegistrationOpen :exec
+INSERT INTO site (registration_open) VALUES (@registration_open)
+ON CONFLICT (id) DO UPDATE SET registration_open = excluded.registration_open;