in src/main/java/software/amazon/msk/auth/iam/internals/MSKCredentialProvider.java [394:410]
StsAssumeRoleCredentialsProvider createSTSRoleCredentialProvider(
String roleArn,
String externalId,
String sessionName,
String stsRegion,
Boolean shouldUseFips) {
AssumeRoleRequest roleRequest = AssumeRoleRequest.builder()
.externalId(externalId)
.roleArn(roleArn)
.roleSessionName(sessionName)
.build();
return StsAssumeRoleCredentialsProvider.builder()
.stsClient(getStsClientBuilder(Region.of(stsRegion), shouldUseFips).build())
.refreshRequest(roleRequest)
.asyncCredentialUpdateEnabled(true)
.build();
}