Stage authenticator_sms: to be able to send the payload within the 'data' request parameter (in addition to the 'json' one)

**Is your feature request related to a problem? Please describe.**
I'm using the authenticator_sms stage with a SMS gateway which does not support the payload in the 'json' parameter.
They only support the 'data' parameter.

I'm pretty sure it is not the only gateway in this case :-)

**Describe the solution you'd like**
It could be nice to add a parameter (example: a checkbox) somewhere in Authentik to decide if we pass the payload as 'data' or 'json'.