[EKS] [request]: Ability to assign access to different EKS clusters, in one AWS account, for different SSO users with same assumed role

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**Tell us about your request**
I need ability to assign different SSO users, which have same assumed role in specific AWS account, to different EKS clusters (over Kubernetes RBAC).

**Which service(s) is this request for?**
EKS

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
What outcome are you trying to achieve, ultimately, and why is it hard/impossible to do right now? What is the impact of not having this problem solved? The more details you can provide, the better we'll be able to understand and solve the problem.

I need the ability to configure more granular access to EKS clusters resources, for SSO users. Right now, to restrict access in EKS cluster, we need create many assumed roles for each user or group of users. As stated in a post on this blog, we can take assumed role ARN, for example arn:aws:sts::111222333444:assumed-role/AWSReservedSSO_EKSClusterAdminAccess_4ffa4321e413c0b0/eksadmin, and modify it to IAM Role ARN, like this - arn:aws:iam::111222333444:role/AWSReservedSSO_EKSClusterAdminAccess_4ffa4321e413c0b0
For example:
**user1** and **user2** SSO users have assumed role **EKSClusterAdminAccess** to AWS account with id **111222333444**, and we need give access for **user1** to EKS cluster **EKS1** and access for **user2** to EKS cluster **EKS2**. We must specify same rolearn string in mapRoles section of aws-auth ConfigMap, in both EKS clusters. In this situation **user1** will have access to clusters **EKS1** and **EKS2**, and user2 have access in same clusters too. An alternative solution could be to assign different assumed roles for different users or group of users in one AWS account, but it would be great to have another approach.

**Are you currently working around this issue?**
Now our team have decided to use an alternative option, with one assumed role per a group of users

**Additional context**
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**Attachments**
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Start by reviewing the EKS access scenario, Kubernetes RBAC requirement, and aws-auth ConfigMap mapRoles example in the issue. Compare the current assumed-role ARN approach with the requested per-user, per-cluster access model; done means establishing a supported way to separate users sharing one AWS role across EKS clusters.

Written by the indexing model from the issue text.