Top-level marker interface defining a ServiceProvider.
A ServiceProvider provides access to a API that the application can invoke on behalf of a provider user.
For example, the FacebookServiceProvider could expose a FacebookApi that the application can invoke on behalf of Facebook user "Keith Donald".
Defines a single parameterized type A representing a strongly-typed Java binding to the provider's API that can be obtained and invoked by the application.
Does not define any operations since the provider authorization flow needed to construct an authorized API binding is protocol specific, for example, OAuth1 or OAuth2.