localstack compatibility for aws providers

[JacobJohansen]

Feature Request

Allow teller to be pointed at localstack for aws_secretsmanager and aws_ssm providers

Is your feature request related to a problem? Please describe.

provide a method to override the default aws endpoint to allow local developers to use the same process as our deployments

Describe the solution you'd like

use the AWS_ENDPOINT environment variable to allow for a custom endpoint to be used with localstack Describe alternatives you've considered

Provider configuration value