[3.x] Switch to `sms()` Client, improved GSM-7 Handling

[SecondeJK]

This PR is a redone version of the previously merged #61, which was reverted because v4.0 of the Vonage Core SDK was not being pulled in. Subsequently, messages were defaulted to Unicode for encoding, resulting in more SMS deliveries to end devices.

This PR now pulls in 4.0.4 of the SDK which does the following:

• Uses the sms() client instead of the legacy message() client.
• Defaults your message type to text which is GSM-7 encoded
• Still enables the user to use the Laravel unicode() method to switch if needs be
• If you send a GSM-7-compatible text as unicode, it will trigger an E_USER_WARNING but no exception, advising you to use the preferred encoding type
• If you send a GSM-7 message that needs to be Unicode, it will trigger an E_USER_WARNING advising you that the end device is likely to have scrambled characters due to not using the preferred encoding type.

For users, if you are not sure of the encoding type for your Notification message, a static helper method is now available for you to check before sending the notification through the channel.

\Vonage\SMS\Message\SMS::isGsm7($message);

Vonage are committed to users and to Laravel itself to make the best developer experience possible. If there are questions or concerns, hit me up.

[driesvints]

Lgtm. @potsky @ankurk91 @Brenneisen would any of you be able to try this one out before we merge it?

[ankurk91]

Sure, tomorrow, my morning 👍

[SecondeJK]

I'll need to do a minor version bump tomorrow morning GMT to squash a bug.

[SecondeJK]

Version bump done.

[ankurk91]

Working fine for me.

[potsky]

Sorry I'm coming after the war but it's good for me too.

@SecondeJK just a feedback : I have no PHP warning if I add the char ç in the message text and ç is not in the default GSM charset.

The message sent with the text type is only in one part and the ç is replace by ? in the received SMS message which is really ok for me.