How do I select only one entry from a lightning:checkboxgroup, meaning, I can do an either - or, but not select two options at once? I have two checkboxes in my group, and v.value gives the order according to the options set in the options attribute, but then I cannot find out which is the latest value selected. See description of lightning:inputcheckbox:<https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/aura_compref_lightning_checkboxGroup.htm>.