NIFI-7497 Adding support for AWS Credentials Assume Role to be able t…

[neptunesalt]

…o set the STS Endpoint

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Description of PR

Enables AWS Credentials to configure Assume Role STS Endpoint functionality; fixes bug NIFI-7497.

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[pvillard31]

Thanks for the contribution @neptunesalt.
LGTM, I'm a +1. I left a comment regarding the description of this new property.

[pvillard31]

Can we add the same comment as in the AWS SDK? Something like:

The default AWS Security Token Service (STS) endpoint ("sts.amazonaws.com") works for all accounts that are not for China (Beijing) region or GovCloud. You only need to set this property to "sts.cn-north-1.amazonaws.com.cn" when you are requesting session credentials for services in China(Beijing) region or to "sts.us-gov-west-1.amazonaws.com" for GovCloud.

[MikeThomsen]

@pvillard31 If that change is the only thing blocking this, I can make it and merge. Let me know if you're +1 on that. We have a use case that really needs this.

[MikeThomsen]

We tested this and confirmed it works. Merging. Thanks for the contribution!