Add support for USSD services by beem.africa

[tuxpiper]

Beem has coverage in several countries and a well-documented API.

https://beem.africa/ussd-api/

ping: @CeciliaHinga

[tuxpiper]

Writing a driver for this shouldn't involve a lot of code

[andrew21-mch]

@tuxpiper please could you help me with a documentation on this, I am not familiar with it but i want to give it a try

[tuxpiper]

Hi @andrew21-mch ! This should be a couple of useful links:

https://docs.beem.africa/ussd/index.html
https://docs.beem.africa/airtime/Ussdsimulator/index.html

[andrew21-mch]

Thanks much, I will take time to go through this

[andrew21-mch]

Hi @tuxpiper please how can i test the USSD Engine