<PackageReference Include="System.ServiceModel.Primitives" Version="6.0.0-rc.23205.4" />

System.ServiceModel.Security.SendSecurityHeaderElementContainer

public void MapSecurityTokenToStrClause(SecurityToken securityToken, SecurityKeyIdentifierClause keyIdentifierClause)

public bool TryGetIdentifierClauseFromSecurityToken(SecurityToken securityToken, out SecurityKeyIdentifierClause keyIdentifierClause)