Adapt this function to the sdk

[todo]

canvas-sdk-php/src/Traits/FileSystemModelTrait.php

Lines 197 to 202 in 51addfc

	* @todo Adapt this function to the sdk
	*
	* @return string|null
	*/
	public function getFileByName(string $fieldName) : ?object
	{

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This issue was generated by todo based on a todo comment in 51addfc when #57 was merged. cc @bakaphp.