@protocol AWSCredentialsProvider <NSObject>
protocol AWSCredentialsProvider : NSObjectProtocol
The AWS credentials provider protocol used to provide credentials to the SDK in order to make calls to the AWS services.
Asynchronously returns a valid AWS credentials or an error object if it cannot retrieve valid credentials. It should cache valid credentials as much as possible and refresh them when they are invalid.
func credentials() -> AWSTask
A valid AWS credentials or an error object describing the error.
Invalidates the cached temporary AWS credentials. If the credentials provider does not cache temporary credentials, this operation is a no-op.