Prompt user when inviting users with uncached identities (#5331)

If the user attempts to invite someone (to a room or creating a DM) whose identity is not cached, we prompt them to make sure this was their intention.

ElementX/Sources/Services/Room/UserToInvite.swift

@@ -0,0 +1,31 @@
+//
+// Copyright 2026 Element Creations Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+// Please see LICENSE files in the repository root for full details.
+//
+
+import Foundation
+
+struct UserToInvite: Identifiable {
+    /// The profile of the user being invited.
+    var user: UserProfileProxy
+    
+    /// The ID of the user being invited.
+    var id: String {
+        user.id
+    }
+    
+    /// Whether we have the cryptographic identity of this user cached locally.
+    var isUnknown: Bool
+    
+    /// The display name of the user being invited
+    var displayName: String? {
+        user.displayName
+    }
+    
+    /// The avatar URL of the user's profile, if available.
+    var avatarURL: URL? {
+        user.avatarURL
+    }
+}