Generic APIs - OTP Provider & template customization

[choxx]

Description

Users of Saksham Samiksha in Haryana while resetting password are receiving OTP messages in the template used for Samagra Shiksha app used in Himachal Pradesh.
https://github.com/Saksham-Education/saksham-samiksha-app/issues/115

We need to allow different applications can use different providers with configurable OTP templates.

Changes

Generic config will be enhanced by adding new JSON fields to allow override OTP provider & template from the default one defined at the environment level.