feat(federations): provide admin setting to enable Federation in Talk

[Antreesy]

☑️ Resolves

• Part of 🌐 Federated invitation handling 💌 - Frontend #11279
  • Add Admin setting section for Federation (in debug mode only)

🖌️ UI Checklist

🖼️ Screenshots / Screencasts

🚧 Tasks

• Check wording

🏁 Checklist

• 🌏 Tested with Chrome, Firefox and Safari or should not be risky to browser differences
• 🖌️ Design was reviewed, approved or inspired by the design team
• 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required

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🛠️ API Checklist

🚧 Tasks

• Check code changes

🏁 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

[nickvergessen]

Should at least hide it when not on debug mode, so we don't forget about it.

Or we default federation to enabled when debug is on, then you also don't need the setting for now, right?

[Antreesy]

Or we default federation to enabled when debug is on, then you also don't need the setting for now, right?

Made changes, now it's visible in debug mode only
I'd keep in configurable anyway. For now it's a good base for putting here new settings, if they'll arise one day.

[DorraJaouad]

Tested and wording is fine.