fix(openId4VP): change input data for calculating transaction_data_hashes

Reason: there was a discussion in openID4VP about how transaction_data_hashes
        have to be calculated. Agreement to use text from v23,
        see openid/OpenID4VP#621

Author: Thomas Lenz

CHANGELOG.md

@@ -8,6 +8,7 @@ Release 5.7.0:
  - OpenID for Verifiable Credential Issuance:
    - Expose `oauth2Client` in `WalletService`
    - Remove code elements deprecated in `5.6.3` in `OpenId4VciClient` 
+   - Update transaction_data_hashes according to result from https://github.com/openid/OpenID4VP/pull/621
  - Holder:
    - Replace `keyPair` with `keyMaterial`
  - Functions:

openid-data-classes/src/commonMain/kotlin/at/asitplus/openid/TransactionData.kt

@@ -2,6 +2,8 @@ package at.asitplus.openid
 
 import at.asitplus.signum.indispensable.io.Base64UrlStrict
 import io.ktor.util.*
+import io.ktor.utils.io.charsets.*
+import io.ktor.utils.io.core.*
 import io.matthewnelson.encoding.core.Decoder.Companion.decodeToByteArray
 import kotlinx.serialization.ContextualSerializer
 import kotlinx.serialization.PolymorphicSerializer
@@ -19,7 +21,7 @@ import okio.ByteString.Companion.toByteString
 typealias TransactionDataBase64Url = JsonPrimitive
 
 fun TransactionDataBase64Url.sha256(): ByteArray =
-    this.content.decodeToByteArray(Base64UrlStrict).toByteString().sha256().toByteArray()
+    this.content.toByteArray(Charsets.UTF_8).toByteString().sha256().toByteArray()
 
 /**
  * OID4VP Draft 24: OPTIONAL. Array of strings, where each string is a base64url encoded JSON object that contains a typed parameter