Don't pass Python Future objects to QML

Returning a Future doesn't work on Windows for some reason
(https://github.com/thp/pyotherside/issues/116).

Instead of using these objects from QML to cancel running coroutines,
call a Python QMLBridge function that takes a coroutine UUID and will
take care of the cancelling.

src/gui/Popups/DeleteDevicesPopup.qml

@@ -4,7 +4,6 @@
 import QtQuick 2.12
 import "../Base"
 import "../Base/Buttons"
-import "../PythonBridge"
 
 PasswordPopup {
     id: popup
@@ -13,15 +12,15 @@ PasswordPopup {
     property var deviceIds  // array
     property var deletedCallback: null
 
-    property Future deleteFuture: null
+    property string deleteFutureId: ""
 
     function verifyPassword(pass, callback) {
-        deleteFuture = py.callClientCoro(
+        deleteFutureId = py.callClientCoro(
             userId,
             "delete_devices_with_password",
             [deviceIds, pass],
             () => {
-                deleteFuture = null
+                deleteFutureId = ""
                 callback(true)
             },
             (type, args) => {
@@ -47,9 +46,9 @@ PasswordPopup {
     validateButton.icon.name: "sign-out"
 
     onClosed: {
-        if (deleteFuture) deleteFuture.cancel()
+        if (deleteFutureId) py.cancelCoro(deleteFutureId)
 
-        if (deleteFuture || acceptedPassword && deletedCallback)
+        if (deleteFutureId || acceptedPassword && deletedCallback)
             deletedCallback()
     }
 }

src/gui/Popups/InviteToRoomPopup.qml

@@ -15,7 +15,7 @@ HColumnPopup {
     property string roomName
     property bool invitingAllowed: true
 
-    property var inviteFuture: null
+    property string inviteFutureId: ""
     property var successfulInvites: []
     property var failedInvites: []
 
@@ -26,12 +26,14 @@ HColumnPopup {
             user => ! successfulInvites.includes(user)
         )
 
-        inviteFuture = py.callClientCoro(
+        inviteFutureId = py.callClientCoro(
             userId,
             "room_mass_invite",
             [roomId, ...inviteesLeft],
 
             ([successes, errors]) => {
+                inviteFutureId = ""
+
                 if (errors.length < 1) {
                     popup.close()
                     return
@@ -61,10 +63,10 @@ HColumnPopup {
     }
 
     onOpened: inviteArea.forceActiveFocus()
-    onClosed: if (inviteFuture) inviteFuture.cancel()
+    onClosed: if (inviteFutureId) py.cancelCoro(inviteFutureId)
 
     onInvitingAllowedChanged:
-        if (! invitingAllowed && inviteFuture) inviteFuture.cancel()
+        if (! invitingAllowed && inviteFutureId) py.cancelCoro(inviteFutureId)
 
     SummaryLabel {
         text: qsTr("Invite members to <i>%1</i>").arg(roomName)