Feat/auth methods

[mamoonraja]

This pull request updates authentication to use Authenticators rather than AuthConfigs. Additionally, legacy authentication logic was removed. Changes to the core essentially followed changes to the dotnet sdk core and I have tried to make a bunch of new changes to Connectors to make sure we match dotnet as closely as possile. I have tested changes with IAM for RestConnector, will do some more testing on other authenticators, and for WSConnector.

We are using branch 1.0.0-rc to stage major release changes. Below is the new snippet for authentication:

IamAuthenticator authenticator = new IamAuthenticator("{apikey}");
AssistantService service = new AssistantService("{versionDate}", authenticator);

Following changes to respective service files will be made:

Constructors:

public AssistantService(string versionDate) : this(versionDate, ConfigBasedAuthenticatorFactory.GetAuthenticator(serviceId)) { }

public AssistantService(string versionDate, Authenticator authenticator) : base(versionDate, authenticator, serviceId)

In methods:

 RESTConnector connector = RESTConnector.GetConnector(authenticator, "/v1/workspaces");
 if (connector == null)
{
     return false;
}

 authenticator.Authenticate(connector);
return connector.Send(req);

[mediumTaj]

I think this is coming together! A few questions here. We prob can get rid of some constructors in the base service. What do you think about moving adding headers to the connectors in the form of WithAuthentication methods?

[mediumTaj]

👍 looks good - just a few minor changes. Approving now though.