Add the ability to require premium fee acking for a registrar

When enabled for a registrar, all EPP operations on premium domains that have
costs (e.g.  creates, renews, transfers) will fail unless the EPP fee extension
is used to explicitly ack the amount of fee as part of the EPP transaction.

This ack is required regardless of whether premium fee acking is required at
the registry level. No data migration is necessary since false is the desired
default for this new attribute.

This CL also contains some slight refactoring of static utility methods used to
perform fee verification; there was short-circuiting at call-sites in two
places when what was really needed was two methods, one implementing additional
functionality on top of the other, and calling the inner method in the places
where short-circuiting had previously been necessary.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=184229363

java/google/registry/flows/domain/DomainFlowUtils.java

@@ -613,20 +613,44 @@ public class DomainFlowUtils {
     }
   }
 
+  /**
+   * Validates that fees are acked and match if they are required (typically for premium domains).
+   *
+   * <p>This is used by domain operations that have an implicit cost, e.g. domain create or renew
+   * (both of which add one or more years' worth of registration). Depending on registry and/or
+   * registrar settings, explicit price acking using the fee extension may be required for premium
+   * domain names.
+   */
   public static void validateFeeChallenge(
       String domainName,
       String tld,
+      String clientId,
       DateTime priceTime,
       final Optional<? extends FeeTransformCommandExtension> feeCommand,
       FeesAndCredits feesAndCredits)
       throws EppException {
+
     Registry registry = Registry.get(tld);
-    if (registry.getPremiumPriceAckRequired()
-        && isDomainPremium(domainName, priceTime)
-        && !feeCommand.isPresent()) {
+    Registrar registrar = Registrar.loadByClientIdCached(clientId).get();
+    boolean premiumAckRequired =
+        registry.getPremiumPriceAckRequired() || registrar.getPremiumPriceAckRequired();
+    if (premiumAckRequired && isDomainPremium(domainName, priceTime) && !feeCommand.isPresent()) {
       throw new FeesRequiredForPremiumNameException();
     }
+    validateFeesAckedIfPresent(feeCommand, feesAndCredits);
+  }
 
+  /**
+   * Validates that non-zero fees are acked (i.e. they are specified and the amount matches).
+   *
+   * <p>This is used directly by update operations, i.e. those that otherwise don't have implicit
+   * costs, and is also used as a helper method to validate if fees are required for operations that
+   * do have implicit costs, e.g. creates and renews.
+   */
+  public static void validateFeesAckedIfPresent(
+      final Optional<? extends FeeTransformCommandExtension> feeCommand,
+      FeesAndCredits feesAndCredits)
+      throws EppException {
     // Check for the case where a fee command extension was required but not provided.
     // This only happens when the total fees are non-zero and include custom fees requiring the
     // extension.
@@ -657,7 +681,7 @@ public class DomainFlowUtils {
       total = total.add(credit.getCost());
     }
 
-    Money feeTotal = null;
+    Money feeTotal;
     try {
       feeTotal = Money.of(feeCommand.get().getCurrency(), total);
     } catch (ArithmeticException e) {