fix(nextjs): improve auth() error message to mention infrastructure failures (#8007)

Co-authored-by: Tom Milewski <me@tm.codes>

Author: jacekradko

.changeset/improve-auth-middleware-error-message.md

@@ -0,0 +1,5 @@
+---
+"@clerk/nextjs": patch
+---
+
+Improved `auth()` error message when `clerkMiddleware()` is not detected to mention that infrastructure issues (e.g. edge runtime errors or platform outages) can also cause this error.

packages/nextjs/src/server/errors.ts

@@ -28,6 +28,8 @@ export const authAuthHeaderMissing = (helperName = 'auth', prefixSteps?: string[
 - Your ${fileReference} matcher is configured to match this route or page.
 - If you are using the src directory, make sure the ${fileReference} file is inside of it.
 
+If you've verified your configuration and are still seeing this error, there may be a runtime issue or a problem communicating with Clerk.
+
 For more details, see https://clerk.com/err/auth-middleware
 `;
 };