feat: add env var for signup flow

constants/routes/signup.ts

@@ -17,3 +17,13 @@ export const signupVerify: LangRoute = {
   da: `${signup.da}/bekraeft`,
   de: `${signup.de}/verifizieren`,
 }
+
+export function isSignupPage(path: string): boolean {
+  const signupPaths = [...Object.values(signup), ...Object.values(signupVerify)]
+  const result = signupPaths.some((signupPath) => {
+    const includes = signupPath.includes(path)
+    return includes
+  })
+
+  return result
+}