* add ability to customize IAM usernames based on templates
* add changelog
* remove unnecessary logs
* patch: add test for readConfig
* patch: add default STS Template
* patch: remove unnecessary if cases
* patch: add regex checks in username test
* patch: update genUsername to return an error instead of warnings
* patch: separate tests for default and custom templates
* patch: return truncate warning from genUsername and trigger a 400 response on errors
* patch: truncate midString to 42 chars in default template
* docs: add new username_template field to aws docs
