MM-16499: Adds ability to retrieve channels with total count f… (#11375)

* MM-16499: Adds ability to retrieve channels with total count for pagination.

* MM-16499: Switches to custom package name for squirrel.

api4/channel_test.go

@@ -832,6 +832,37 @@ func TestGetAllChannels(t *testing.T) {
 	CheckForbiddenStatus(t, resp)
 }
 
+func TestGetAllChannelsWithCount(t *testing.T) {
+	th := Setup().InitBasic()
+	defer th.TearDown()
+	Client := th.Client
+
+	channels, total, resp := th.SystemAdminClient.GetAllChannelsWithCount(0, 20, "")
+	CheckNoError(t, resp)
+
+	// At least, all the not-deleted channels created during the InitBasic
+	require.True(t, len(*channels) >= 3)
+	for _, c := range *channels {
+		require.NotEqual(t, c.TeamId, "")
+	}
+	require.Equal(t, int64(5), total)
+
+	channels, _, resp = th.SystemAdminClient.GetAllChannelsWithCount(0, 10, "")
+	CheckNoError(t, resp)
+	require.True(t, len(*channels) >= 3)
+
+	channels, _, resp = th.SystemAdminClient.GetAllChannelsWithCount(1, 1, "")
+	CheckNoError(t, resp)
+	require.Len(t, *channels, 1)
+
+	channels, _, resp = th.SystemAdminClient.GetAllChannelsWithCount(10000, 10000, "")
+	CheckNoError(t, resp)
+	require.Len(t, *channels, 0)
+
+	_, _, resp = Client.GetAllChannelsWithCount(0, 20, "")
+	CheckForbiddenStatus(t, resp)
+}
+
 func TestSearchChannels(t *testing.T) {
 	th := Setup().InitBasic()
 	defer th.TearDown()