Support Sigv4 Auth

[ryanakann]

SigV4 (Signature Version 4) is an authentication process that allows AWS services to identify requests made using your security credentials and verify that the request sender is authorized to access resources in your AWS account. [1]

SigV4 authentication works with IAM to securely identify the sender of AWS API requests and verify they have permission to access AWS resources based on their signed identity and assigned policies. This helps ensure only authorized access occurs in your AWS account.

By allowing Sigv4, this plugin may support an IAM role similar to how the CloudWatch Data Source does.