### Motivation
We need to be able to change annotation to inject AWS IAM role (EKS based deployment).
https://docs.aws.amazon.com/eks/latest/userguide/specify-service-account-role.html
With 2.6.0 and this annotation change we were able to use Tiered Storage with S3 and EKS/IAM(OIDC).
e.g :
```
annotations:
eks.amazonaws.com/role-arn: arn:aws:iam::66666:role/my-iam-role-with-s3-access
```
values.yaml
```
broker:
service_account:
annotations:
eks.amazonaws.com/role-arn: arn:aws:iam::66666:role/my-iam-role-with-s3-access
```
### Modifications
Added a value to allow to change annotations fro broker service account.
I've tried following style from other part of the code.
### Verifying this change
- [ ] Make sure that the change passes the CI checks.
6cddb81da1