Checkbox
The value of the checkbox is set based on the checkbox state. If checked, then it is true, otherwise false. Please note that input should have form-input class.
<input type="checkbox" id="formInputOnlineAppointmentsEnabled" class="form-input"
name="AccountAdminApi.WarehouseInput.OnlineAppointmentsEnabled"
{{ if .Data.AccountAdminApi.WarehouseInput.OnlineAppointmentsEnabled }} checked {{ end }}>
<!-- if not checked, passed hidden field, otherwise both but first one have higher priority (FIFO) -->
<input type="hidden" name="AccountAdminApi.WarehouseInput.OnlineAppointmentsEnabled" value="false">
<label for="formInputOnlineAppointmentsEnabled">Online appointments</label>