Missing support for AWS_SESSION_TTL and AWS_ASSUME_ROLE_TTL in env and write-to-credentials

[chizou]

The options env and write-to-credentials don't seem to have the calls to loadDurationFlagFromEnv that the exec option seems to have. This is breaking some of our use cases. Can it be added to bring env and write-to-credentials on parity with exec?

[chizou]

They also seem to be lacking support for the assume_role_ttl option in the config file

[j0nathontayl0r]

Yeah I've just came across this problem @chizou.

If you use the -t flag when using the CLI though, the TTL is honoured.

E.g.

aws-okta exec AnAWSAccount-Profile -t 12h -- code 

[nickatsegment]

Wontfix #278