optionValue support for p-treeSelect

[puschie286]

Would be nice to have an optionValue property (like in all other select components).

Currently, selection gives you a TreeNode or TreeNode[]. This makes it pretty complicated to be used within an reactive form.

The only solution i see right know is to create transform method for each treeSelect (and mark element as standalone with ngModelOptions )

[puschie286]

helper function:

export function getNodeFromKey( key?: string, nodes?: TreeNode[] ): TreeNode | undefined
{
	if( key == undefined || nodes == undefined || nodes.length === 0 )
	{
		return undefined;
	}

	for( const entry of nodes )
	{
		// hit ?
		if( entry.key === key )
		{
			return entry;
		}

		// level down
		const found = getNodeFromKey( key, entry.children );
		if( found != undefined )
		{
			return found;
		}
	}

	return undefined;
}