[REQ] Use AWS STS regional endpoint instead of AWS Global Endpoint by default

Is your feature request related to a problem? Please describe.
I am from EKS team, for some EKS clusters where cuatomers are using OpenAPI-Generator we have observed this user-agent OpenAPI-Generator/29.0.0/python defaults to using global STS endpoint rather than the regional STS endpoint.

It is recommended to use the AWS regional endpoint rather than the global endpoint. This ensures better performance and compliance with AWS best practices.
https://docs.aws.amazon.com/sdkref/latest/guide/feature-sts-regionalized-endpoints.html

Describe the solution you'd like
We propose use the AWS regional STS endpoint by default instead of the global endpoint to enhance performance, reduce latency, and align with AWS best practices.

Additional context
Switching to regional endpoints can improve response times, reduce load on the global endpoint, and follow best practices for optimized resource usage.

Note
If you think this is irrelevant feel free to close this issue.

Start with the issue body and the linked AWS regionalized-endpoints guidance, then locate the generator entry point that sets the STS endpoint default for the affected Python output. Done means generated clients use the regional endpoint by default; no file or test is named, so repository investigation is required.