[Admin Tool Feature]: Notify recipients to confirm payment

[mkue]

Recipients should receive a message (sms) as soon as the payments have been sent (through button in admin tool).

The sms should be sent to the orange money phone number.

The message should be stored in a subcollection of the user (/recipients/{id}/messages). Also, a reference field (message) should be added to the payment. A user should never receive a message for a payment twice, i.e. the message shouldn't be sent if the reference field is already set.