clients library Null safety

Classes

ApiRestClient
Client for api requests
AuthRestClient
Client for authentication
BearerHttpClient
http_interceptors don't support send() yet. This is an easy solution, to inject the token from the outside, while keeping the the interceptor logic working
RestClient
Wrapper for Http client to be used for requests to a specific host A bearer token can be set, which will be appended to each request
SpeechPackageRestClient
Client for speech pack requests