How to use Keycloak with SQL Server

[christiannagel]

What needs to be done to run keycloak using SQL Server successfully? I've tried this app-model specifying the connection string as used by #6084

var sqlServer = builder.AddSqlServer("keycloaksql")
    .WithDataVolume("keycloakdata");

var sqlDb = sqlServer.AddDatabase("keycloakdb", "keycloakidentity");

var keycloak = builder.AddKeycloak("keycloak")
    .WithEnvironment(context =>
    {
        context.EnvironmentVariables.Add("KC_DB", "mssql");
        context.EnvironmentVariables.Add("KC_DB_URL", 
            $"jdbc:sqlserver://{sqlServer.Resource.PrimaryEndpoint.ContainerHost};databaseName={sqlDb.Resource.DatabaseName};trustServerCertificate=true;user=sa;password={sqlServer.Resource.PasswordParameter.Value};");
    })
    .WaitFor(sqlDb);

Keycloak fails with this error:

[org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator] (JPA Startup Thread) HHH000342: Could not obtain connection to query metadata: java.lang.NullPointerException: Cannot throw exception because the return value of "java.util.function.BiFunction.apply(Object, Object)" is null

Did I miss any configuration required with Keycloak?