azure-ad-b2c - SubJourney "80131515: ValidateAsync is not supported for Web.TPEngine.Providers.RestfulProvider" 内で実行された場合の SAML TechnicalProfile からのエラー

Question

このガイドに従って、Azure AD B2C で SAML IDP を設定しています。UserJourney で OrchestrationStep として実行すると問題なく動作しますが、SubJourney の一部として実行すると、次の例外が発生します。

[
  {
    "Kind": "Headers",
    "Content": {
      "UserJourneyRecorderEndpoint": "urn:journeyrecorder:applicationinsights",
      "CorrelationId": "<removed>",
      "EventInstance": "Event:ClaimsExchange",
      "TenantId": "<removed>",
      "PolicyId": "<removed>"
    }
  },
  {
    "Kind": "Transition",
    "Content": {
      "EventName": "ClaimsExchange",
      "StateName": "Initial"
    }
  },
  {
    "Kind": "Predicate",
    "Content": "Web.TPEngine.StateMachineHandlers.ClaimsExchangeMessageValidationHandler"
  },
  {
    "Kind": "FatalException",
    "Content": {
      "Time": "4:03 PM",
      "Exception": {
        "Kind": "Handled",
        "HResult": "80131515",
        "Message": "ValidateAsync is not supported for Web.TPEngine.Providers.RestfulProvider",
        "Data": {}
      }
    }
  }
]

機能する OrchestrationStep

<OrchestrationStep Order="3" Type="ClaimsExchange">
  <ClaimsExchanges>
    <ClaimsExchange Id="MySamlExchange" TechnicalProfileReferenceId="my-saml-idp-SAML2" />
  </ClaimsExchanges>
</OrchestrationStep>

エラーを生成する OrchestrationStep

<OrchestrationStep Order="3" Type="InvokeSubJourney" >
  <JourneyList>
    <Candidate SubJourneyReferenceId="SamlFederationJourney" />
  </JourneyList>
</OrchestrationStep>

...

<SubJourneys>
  <SubJourney Id="SamlFederationJourney" Type="Call">
    <OrchestrationSteps>
      <OrchestrationStep Order="1" Type="ClaimsExchange">
        <ClaimsExchanges>
          <ClaimsExchange Id="MySamlExchange" TechnicalProfileReferenceId="my-saml-idp-SAML2" />
        </ClaimsExchanges>
      </OrchestrationStep>
    </OrchestrationSteps>
  </SubJourney>
</SubJourneys>