fix(nuxt): allow modules to disable appManifest without crashing

[IonianPlayboy]

🔗 Linked issue

• Disabling experimental.appManifest in a module breaks the app #24672

❓ Type of change

• 📖 Documentation (updates to the documentation, readme or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Resolves #24672

nuxt.options.experimental.appManifest is set to true by default, and can be set to false by users if they want to opt out of the app manifest generation feature. However, a user module trying to disable appManifest would break completely the user app because of the ordering in initNuxt (located in packages/nuxt/src/core/nuxt.ts).

Before this PR, the manifest-route-rule middleware was added before any user module could have the opportunity to set nuxt.options.experimental.appManifest to false. However, the middleware throws an error if it is registered and appManifest is not equal to true.

As a result, when a user module tried to override the Nuxt config to set nuxt.options.experimental.appManifest to false, the middleware was still registered in the app but was throwing on every route with a 500 error, thus broking the app.

This is why this PR moves the addition of the manifest-route-rule middleware after the registration of user hooks : this way, the config can be altered by the user modules before the middleware is added.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

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[IonianPlayboy]

For the record, I tried to add a test to cover this bug for the future, but I was not sure how exactly the test setup worked and I did not find the time to dive further into it. If this is something you consider worthwile for this PR, I would appreciate some guidance about how to do it.

[danielroe]

Sorry about all the spam - just making a one line change on my phone 😅