Add in notes about support for KeyColumn parameter when using option group as...

Add in notes about support for KeyColumn parameter when using option group as part of a setting pseudoconstant

docs/framework/setting.md

@@ -63,7 +63,7 @@ The Supported Properties for settings are:
 | `html_type` | Html type (admin form)| This is the preferred way to describe the html type as it is not quick form specific. It will be used it present. Syntax is lower case. e.g 'select', 'radio', 'checkboxes', 'checkbox', 'text', 'textarea', 'entity_reference|
 | `quick_form_type` | Widget type (admin form)| YesNo, CheckBox, CheckBoxes, Select, EntityRef. This is not required if html_type (preferred) is set|
 |`settings_pages`|Admin Pages to render this setting on|e.g  ['event' => ['weight' => 10]]. This works if the Generic form is used (see further down)|
-|`pseudoconstant`|Provides information to build a list of available options| This is the perferred methodology for lists of options and currently supports either a callback - e.g ```['callback' => 'CRM_Core_SelectValues::geoProvider']``` or an option group name [`'optionGroupName' => 'advanced_search_options'`]. It does not currently support the full range of values for this key that the DAO schema does, by ommission rather than design|
+|`pseudoconstant`|Provides information to build a list of available options| This is the preferred methodology for lists of options and currently supports either a callback - e.g ```['callback' => 'CRM_Core_SelectValues::geoProvider']``` or an option group name [`'optionGroupName' => 'advanced_search_options'`]. As in the case of the DAOs you can also when specifying an `optionGroupName` you can specify `keyColumn` which specifies which column within `civicrm_option_value` to use as the key, by default this will be the value column. It does not currently support the full range of values for this key that the DAO schema does, by ommission rather than design|
 |`options`|provides an array of available options|This is not the preferred methodology but make make sense for very simple lists. |
 |`entity_reference_options`|extra data to pass when adding an entity reference|e.g if the entity is not contact this make be needed as in `['entity' => 'group', 'select' => array('minimumInputLength' => 0)]`|
 |`documentation_link`|Array of information to build the 'learn more' link| 'page' is required, if on the wiki 'resource' is also needed - e.g 'documentation_link' => ['page' => 'Multi Site Installation', 'resource' => 'wiki'],|