Feature: Aggregate over Arrays / via ArrayDataSource

[alex-kalanis]

Greetings,

is it possible to accept ArrayDataSource|array as another type in \Contributte\Datagrid\AggregationFunction\IAggregationFunction::processDataSource() ?

Then to \Contributte\Datagrid\DataSource\ArrayDataSource something like following:

	public function processAggregation(IAggregationFunction $function): void
	{
		$function->processDataSource($this);
	}

And then into \Contributte\Datagrid\AggregationFunction\FunctionSum::processDataSource following part:

		if ( $dataSource instanceof ArrayDataSource) {
			foreach( $dataSource->getData() as $item )
				$this->result += $item[$this->column];
		}

		if ( is_array($dataSource)) {
			foreach( $dataSource as $item )
				$this->result += $item[$this->column];
		}

Use case:

Due sheer completness of dataset we cannot access the data from it directly via SQL, so we pre-calculate it in parts and then use it with aggregation. That makes us dependent on arrays / ArrayDataSource. And due limitation of other parts of Datagrid we must store its affected files locally and overwrite them on deploy.

Do you want PR? Discuss.

Thanks.