private async void btnUgovoriCas_Click(object sender, EventArgs e)
        {
            var frmNoviCas = new frmCasDetalji(id, instanca.Pocetak.Date);
            var dialog     = frmNoviCas.ShowDialog();

            if (dialog == DialogResult.OK)
            {
                await LoadKurs();
            }
        }
        private async void gridCasovi_MouseDoubleClick(object sender, MouseEventArgs e)
        {
            int casId      = (int)gridCasovi.SelectedRows[0].Cells[gridCasovi.Columns[nameof(CasModel.Id)].Index].Value;
            var frmCasEdit = new frmCasDetalji(id, instanca.Pocetak.Date, casId);
            var dialog     = frmCasEdit.ShowDialog();

            if (dialog == DialogResult.OK)
            {
                await LoadKurs();
            }
        }