Fix Astro middleware by collapsing duplicate leading slashes in URL path

Fixes the following worker crash in Cloudflare Pages when accessing an
API endpoint where the URL path starts with more than one slash:

    (error) 19:51:47 [ERROR] TypeError: Invalid URL string.
      at new ClerkUrl (_astro-internal_middleware.mjs:2383:16)
      at createClerkUrl (_astro-internal_middleware.mjs:2389:10)
      at ClerkRequest.deriveUrlFromHeaders (_astro-internal_middleware.mjs:2420:12)
      at new ClerkRequest (_astro-internal_middleware.mjs:2395:26)
      at createClerkRequest (_astro-internal_middleware.mjs:2434:54)
      at astroMiddleware (_astro-internal_middleware.mjs:3657:26)
      at applyHandle (chunks/index_CJfit7_z.mjs:353:22)
      at chunks/index_CJfit7_z.mjs:372:18
      at _astro-internal_middleware.mjs:3902:26
      at applyHandle (chunks/index_CJfit7_z.mjs:353:22)

packages/backend/src/tokens/__tests__/clerkRequest.test.ts

@@ -151,6 +151,11 @@ export default (QUnit: QUnit) => {
         });
         assert.equal(createClerkRequest(req).clerkUrl.toString(), 'https://example.com/path?foo=bar');
       });
+
+      it('should collapse duplicate leading slashes in URL path', assert => {
+        const req = new Request('http://localhost:3000///path');
+        assert.equal(createClerkRequest(req).clerkUrl.toString(), 'http://localhost:3000/path');
+      });
     });
 
     module('toJSON', () => {

packages/backend/src/tokens/clerkRequest.ts

@@ -46,12 +46,13 @@ class ClerkRequest extends Request {
     const forwardedHost = req.headers.get(constants.Headers.ForwardedHost);
     const host = req.headers.get(constants.Headers.Host);
     const protocol = initialUrl.protocol;
+    const sanitizedPath = initialUrl.pathname.replace(/^\/+/g, '/')
 
     const resolvedHost = this.getFirstValueFromHeader(forwardedHost) ?? host;
     const resolvedProtocol = this.getFirstValueFromHeader(forwardedProto) ?? protocol?.replace(/[:/]/, '');
     const origin = resolvedHost && resolvedProtocol ? `${resolvedProtocol}://${resolvedHost}` : initialUrl.origin;
 
-    return createClerkUrl(initialUrl.pathname + initialUrl.search, origin);
+    return createClerkUrl(sanitizedPath + initialUrl.search, origin);
   }
 
   private getFirstValueFromHeader(value?: string | null) {