feat: better error handling for oidc api key

This also ships with a better error page

app/server/headscale/api/error-client.ts

@@ -0,0 +1,57 @@
+import type { HeadscaleConnectionError } from './error';
+
+/**
+ * Represents an error returned by the Headscale API.
+ */
+export interface HeadscaleAPIError {
+	requestUrl: `${string} ${string}`;
+	statusCode: number;
+	rawData: string;
+	data: Record<string, unknown> | null;
+}
+
+/**
+ * Type guard to check if an error is a HeadscaleAPIError.
+ * @param error - The error to check.
+ * @returns True if the error is a HeadscaleAPIError, false otherwise.
+ */
+export function isApiError(error: unknown): error is HeadscaleAPIError {
+	return (
+		error != null &&
+		typeof error === 'object' &&
+		'requestUrl' in error &&
+		'statusCode' in error &&
+		'rawData' in error &&
+		'data' in error
+	);
+}
+
+/**
+ * Type guard to check if an error is a HeadscaleConnectionError.
+ * @param error - The error to check.
+ * @returns True if the error is a HeadscaleConnectionError, false otherwise.
+ */
+export function isConnectionError(
+	error: unknown,
+): error is HeadscaleConnectionError {
+	return (
+		error != null &&
+		typeof error === 'object' &&
+		'requestUrl' in error &&
+		'errorCode' in error &&
+		'errorMessage' in error &&
+		'extraData' in error
+	);
+}
+
+export function isDataUnauthorizedError(error: unknown): boolean {
+	return (
+		error != null &&
+		typeof error === 'object' &&
+		'data' in error &&
+		typeof error.data === 'object' &&
+		error.data != null &&
+		'statusCode' in error.data &&
+		error.data.statusCode === 401
+	);
+}