Correctly handle account with invalid access token

Show a popup saying the session was signed out and cleanup
the models data, instead of spamming the users with
never-ending errors.

src/gui/Popups/InvalidAccessTokenPopup.qml

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+
+import QtQuick 2.12
+import "../Base"
+import "../Base/Buttons"
+
+HFlickableColumnPopup {
+    id: popup
+
+    property string userId
+
+    signal signBackInRequest()
+
+    page.footer: AutoDirectionLayout {
+        ApplyButton {
+            id: signBackButton
+            text: qsTr("Sign back in")
+            icon.name: "sign-back-in"
+            onClicked: {
+                const page = "Pages/AddAccount/AddAccount.qml"
+                window.mainUI.pageLoader.show(page)
+                popup.close()
+            }
+        }
+
+        CancelButton {
+            text: qsTr("Close")
+            onClicked: popup.close()
+        }
+    }
+
+    SummaryLabel {
+        text: qsTr("Signed out from %1").arg(coloredNameHtml("", userId))
+        textFormat: SummaryLabel.StyledText
+    }
+
+    DetailsLabel {
+        text: qsTr(
+            "You have been disconnected from another session, " +
+            "by the server for security reasons, or the access token in " +
+            "your configuration file is invalid."
+        )
+    }
+
+    onOpened: signBackButton.forceActiveFocus()
+}