* fix: named addresses must be surrounded by double quotes
Due to your recent API update, named addresses with special chars (like parentheses) are now rejected if they are surrounded by simple quotes
They must be surrounded by double quotes
'Whoever (SomeCompany)' <some@address.com> is no longer valid and will be rejected by your API
"Whoever (SomeCompany)" <some@address.com> is valid and will be OK
* sprintf instaead of old school concatenation
* Bug fix - Allow adding custom headers with non-array value
* Remove whitespace
* Functional test for adding custom headers (either singular or multiple)
* Style fixes for functional test
* Write test to verify expected behaviour when we provide a String
* Fix broken test checking if the variable is an Array
* PSR Standard using single quote instead of double quote
