* update genUsername to cap STS usernames at 64 chars
* add changelog
* refactor tests into t.Run block
* patch: remove warningExpected bool and include expected string
* patch: revert sts to cap at 32 chars and add assume_role case in genUsername
* update changelog
* update genUsername to return error if username generated exceeds length limits
* update changelog
* add conditional default username template to provide custom STS usernames
* update changelog
* include test for failing STS length case
* update comments for more clarity
* 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
