model: Add get_all_subscription_ids accessor method.

This commit adds the subscription ids accessor method
"get_all_stream_ids". This helps in preparation for including
subscription color accessor method added in the next commit.

Tests added.

Author: theViz343

tests/model/test_model.py

@@ -2088,6 +2088,15 @@ def test_is_stream_invite_only(
         assert model.is_stream_invite_only(stream_id) == expected_value
         model._get_stream_from_id.assert_called_once()
 
+    def test_get_all_subscription_ids(
+        self,
+        model,
+        stream_dict,
+        expected_value=[1000, 99, 999, 1, 2],
+    ):
+        model.stream_dict = stream_dict
+        assert model.get_all_subscription_ids() == expected_value
+
     @pytest.mark.parametrize("muted", powerset([99, 1000]))
     @pytest.mark.parametrize("visual_notification_enabled", powerset([99, 1000]))
     def test__subscribe_to_streams(

zulipterminal/model.py

@@ -1192,6 +1192,9 @@ def get_all_stream_ids(self) -> List[int]:
         id_list.extend(stream_id for stream_id in self._never_subscribed_streams)
         return id_list
 
+    def get_all_subscription_ids(self) -> List[int]:
+        return list(self.stream_dict)
+
     def get_stream_name(self, stream_id: int) -> str:
         return self._get_stream_from_id(stream_id)["name"]