Give more options on default header by passing an array.

[todo]

zohocrm/src/Zoho/CRM/ZohoClient.php

Lines 356 to 361 in cd680ff

	* @todo Give more options on default header by passing an array.
	*/
	public function getDefaultHeaders()
	{
	$this->generateAccessTokenByRefreshToken();
	return [

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This issue was generated by todo based on a @todo comment in cd680ff when #41 was merged. cc @mctekk.