public String getAuthenticationProviderIdentifier()
            throws GuacamoleException {
        return getRequiredParameter(AUTH_PROVIDER_IDENTIFIER_PARAMETER);
    }
Returns the identifier of the AuthenticationProvider associated with the
UserContext from which the connection or connection group is to be
retrieved when the tunnel is created. In the context of the REST API and
the JavaScript side of the web application, this is referred to as the
data source identifier.

@return
    The identifier of the AuthenticationProvider associated with the
    UserContext from which the connection or connection group is to be
    retrieved when the tunnel is created.

@throws GuacamoleException
    If the identifier was not present in the request.
guacamole/src/main/java/org/apache/guacamole/tunnel/TunnelRequest.java