New Messaging callbacks parameter available for select channels

Who is affected: Messaging customers
Products affected: Messaging - MMS, RCS, Email, and SMS
Changes:
- New Messaging callbacks parameter:  A new Messaging callbacks parameter identifies the channel used for an end user's response - ideal for situations when the same Mobile Originated (MO) Callback URL is used for more than one channel. This simplifies using one MO Callback URL for an integration. The new parameter sub_resource returns a value that lists the specific channel used when an end user replies with a suggested action or by sending an inbound message. For example, if the end user's response is via the RCS channel, sub_resource returns the value mo_rcs. The values for each channel are listed below:
- MMS: mo_mms
- RCS: mo_rcs
- Email: mo_email
- SMS: mo_sms