toIdOf in SOQL Cache [release v6.8.0]

[pgajek2]

Is your feature request related to a problem? Please describe.
The toValueOf method should automatically add used field to the SELECT clause.

// before
SOQLCache.of('Account').with(Account.Industry).toIdOf(Account.CreatedById);

// after
SOQLCache.of('Account').toIdOf(Account.CreatedById);