fix(openapi): openapi.json ignores custom port

[hanspagel]

🔗 Linked issue

#2215

❓ 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

Currently, we’re using a hard coded string (http://localhost:3000) for the base url that is added to the openapi.json. If a custom port is configured, it’s just ignored. This PR fixes it by using the same logic that is used in other places:

• Use process.env.NITRO_PORT, if it’s not available:
• Use process.env.PORT, if it’s not available:
• Fallback to port 3000 (the default)

While I was on it, I’ve also removed the trailing slash from the base URL. It’s not really needed, as all routes start with a / already, but it looks cleaner. ✨

📝 Checklist

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

[pi0]

Thanks for PR dear @hanspagel. It is fixed via #2216 (with incoming port)