Add user registration configuration option to environment settings

server/env.example

@@ -66,6 +66,10 @@ JWT_ACCESS_EXPIRES_IN=15m
 # Refresh Token 过期时间
 JWT_REFRESH_EXPIRES_IN=7d
 
+# 注册配置
+# 是否开放用户注册 (true/false)
+ALLOW_REGISTRATION=true
+
 # ----------------------------------------
 # CORS 跨域配置
 # ----------------------------------------