refactor: remove some duplicated code

lib/errors.ts

@@ -0,0 +1,25 @@
+import { MiddlewareHandlerContext } from "$fresh/server.ts";
+
+class DomainError extends Error {
+  status = 500;
+  render?: (ctx: MiddlewareHandlerContext) => void;
+  constructor(public statusText = "Internal Server Error") {
+    super();
+  }
+}
+
+class NotFoundError extends DomainError {
+  status = 404;
+  constructor(public statusText = "Not Found") {
+    super();
+  }
+}
+
+class BadRequestError extends DomainError {
+  status = 400;
+  constructor(public statusText = "Bad Request") {
+    super();
+  }
+}
+
+export { BadRequestError, DomainError, NotFoundError };