Provide default value for `requiredClaims`

[angiejones]

Issue

Currently, even if a developer is creating an offering that doesnt have any required claims, they still have to add the requiredClaims value to their object. This is because, while OfferingData does have requiredClaims as optional, there's no default value. So this forces developers to pass in null to get around this.

Current usage

      OfferingData(
          description = "Selling GBP for USD",
          payin = PayinDetails(currencyCode = "USD", methods = listOf()),
          payout = PayoutDetails(currencyCode = "GBP", methods = listOf()),
          payoutUnitsPerPayinUnit = "0.00003826",
          requiredClaims = null
      )

Desired usage

      OfferingData(
          description = "Selling GBP for USD",
          payin = PayinDetails(currencyCode = "USD", methods = listOf()),
          payout = PayoutDetails(currencyCode = "GBP", methods = listOf()),
          payoutUnitsPerPayinUnit = "0.00003826"
      )

Suggested Fix

Update ResourceData to:

val requiredClaims: PresentationDefinitionV2? = null