NewAWSAuth initializes a new AWS auth method interface to be passed as a parameter to the client.Auth().Login method.

WithIdentitySignature will have the client send the cryptographic identity document signature to verify EC2 auth logins.

WithNonce can be used to specify a named nonce for the ec2 auth login method.

WithPKCS7Signature will explicitly tell the client to send the PKCS #7 signature to verify EC2 auth logins.

WithRSA2048Signature will explicitly tell the client to send the RSA2048 signature to verify EC2 auth logins.