fix(conversation): allow to invite federated user when creating a conversation

[Antreesy]

☑️ Resolves

• allow to invite federated user when creating a conversation
• conversation creation flow seems to work without errors (with stable network)

🖼️ Screenshots / Screencasts

Avatar is only shown, if user is joined to the room, which can proxy this exact avatar from remote server

• LeftSidebar search also returns federated user as an option, but doesn't show it (something for later - private federeated conversation?)

🏁 Checklist

• 🌏 Tested with Chrome, Firefox and Safari or should not be risky to browser differences
• 🖥️ Tested with Desktop client or should not be risky for it