Add json.Number parsing for iam_request_header values (#3770)
Add json.Number parsing for iam_request_header values (#3770)

Fixes #3763
joelthompson/vault,hartsock/vault,mgk/vault,hashicorp/vault,quixoten/vault,Aloomaio/vault,joelthompson/vault,mgk/vault,hashicorp/vault,rnaveiras/vault,kingland/vault,hashicorp/vault,quixoten/vault,mgk/vault,naunga/vault,joelthompson/vault,kingland/vault,kingland/vault,Aloomaio/vault,joelthompson/vault,hartsock/vault,hartsock/vault,quixoten/vault,hashicorp/vault,hashicorp/vault,hartsock/vault,Aloomaio/vault,kingland/vault,quixoten/vault,Aloomaio/vault,naunga/vault,rnaveiras/vault,hartsock/vault,hashicorp/vault,rnaveiras/vault,kingland/vault,mgk/vault,rnaveiras/vault,rnaveiras/vault