fix(federation)!: Add room name to invite and fix casing of properties

[nickvergessen]

☑️ Resolves

• Ref 🌐 Federated invitation handling 💌 - API #11278 (comment)

🛠️ API Checklist

🚧 Tasks

• Add room name and document state
• Change from _ casing to camelCase like on all other APIs

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not possible
• 📘 API documentation in docs/ has been updated or is not required
• 🔖 Capability is added or not needed

[SystemKeeper]

Just by looking at the code, it is correct that jsonSerialize does not contain roomName?

[SystemKeeper]

Not related to this PR but tests show

[4131] [Thu Feb  1 07:58:31 2024] {"app":"PHP","message":"Undefined array key \"silent\" at \/home\/runner\/work\/spreed\/spreed\/apps\/spreed\/lib\/Model\/Message.php#224"}

[nickvergessen]

Just by looking at the code, it is correct that jsonSerialize does not contain roomName?

It can not, as that is not stored in the invitation table

[SystemKeeper]

Tested and works