Using Role Assumer in tf-next

[gipsen92]

Hello Felix,

first of thanks for this project, really interesting. we are starting using it here in france.
We encountered an issue while deploying our app, because we assume role on our CI and it seems that it is not supported in your project.
Would you be interesting in having this feature included in your lib or you skipped it on purpose. Spoiler we added @aws-sdk/client-sts module which is not trivial.

Best, Guillaume.