adding enrolled-when_selected to the category form, and improviing validation
adding enrolled-when_selected to the category form, and improviing validation

izzyalonso/tndata_backend,izzyalonso/tndata_backend,tndatacommons/tndata_backend,tndatacommons/tndata_backend,tndatacommons/tndata_backend,tndatacommons/tndata_backend,izzyalonso/tndata_backend,izzyalonso/tndata_backend