Support for setting DurationSeconds(MaxSessionDuration) during AssumeRoleWithSaml

[Junglists]

It would be great if we can specify the DurationSeconds parameter as MaxSessionDuration while assuming the role. Currently the code uses the default 1 hour which is also the IAM role default. However we can set the MaxSessionDuration for a IAM Role to be maxed at 12 hours

Creating an optional parameter which will be defaulted to 1 would be ideal. When providing a DurationSeconds bigger than MaxSessionDuration then we would overwrite the DurationSeconds parameter with MaxSessionDuration retrieved from role details.