* 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
