Add util for adding age_over_NN claims

[TimoGlastra]

Comment from old code:

// TODO:
//
// This should be calculated from the `validFrom` field in device retrieval
// and the `iat` from server retrieval. Not `Date.now()`
//
// In case of device retrieval, the value of an age_over_NN data element
// shall be calculated by the issuing authority infrastructure to be valid
// at the value of the timestamp in the validFrom element in the MSO
// from 9.1.2.4. In case of server retrieval, the value of an age_over_NN
// data element shall be valid at the value of the iat timestamp as
// defined in 8.3.2.2.2.2 and 8.3.3.2.2.