JWT Profile for OAuth 2.0 Client Authentication and Authorization Grants

**Is your feature request related to a problem? Please describe.**
There is no support for using JWT as a client_assertion for getting an access token.

**Describe the solution you'd like**
Currently the client library allows for client secret based authentication. I would like to support JWT, according to RFC7523: https://tools.ietf.org/html/rfc7523.

In particular, this is used for server to server authentication with many EMR (Electronic Medical Record) systems.

I have an implementation ready for a PR, implemented as a HttpExecuteInterceptor, as done in ClientParametersAuthentication

**Describe alternatives you've considered**
I could implement this using raw HTTP client such as OKHttp. In fact, I have an working implementation.

**Additional context**