Adding RecipientHandlerTranslationRestricted to support sending newsletter...

Omar Mohamad - El Hassan Lopesinorequested to merge
issue/simplenews-1551752:1551752-multilingual-improvements-4.x into 4.x

Adding RecipientHandlerTranslationRestricted to support sending newsletter issues only to subscribers with the preferred language matching an existing translation of the issue

Closes #1551752

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