Unicode option on all SMS endpoints

It's now posible to define special characters as non-unicode. Whenever the flag is set to false any unicode characters in the message payload will be converted to their english equivalents.

Example characters that are considered unicode
À  â È Ê ê Ë ë Î î Ï ï Ô ô Œ œ Ù Û û Ÿ ÿ ç

Endpoints supporting this change:

     "unicodeEnabled": true,
     "name": "RecipientName",
     "sender": "Sendinblue Inc.",
     "content": "Message body containing unicode characters À Â â È Ê"