ID4142: The SAML2:Assertion is signed but the signature's KeyIdentifier cannot be resolved to a SecurityToken. Ensure that ...

ID4142: The SAML2:Assertion is signed but the signature's KeyIdentifier cannot be resolved to a SecurityToken. Ensure that the appropriate SecurityTokenResolver has been provisioned. To handle advanced token resolution requirements, extend Saml2SecurityTokenHandler and override ResolveIssuerToken.