Generic field that can be used to store generic info
This generic field can contain up to 20 key-value items with a maximum length of 45 for the key and of 500 chars for the value.
Metadata can be defined when using the Create payment or the Create authorization and then it can be changed at any time using the Update a payment or the Update authorization.
The field phone_number can be defined to pre-fill the mobile number when using the Create payment or the Create authorization.