Set EAP billing event to one-year period

This is consistent with how we treat RESTORE billing events as well- in
general, fees are considered to be amortized over the course of a year (by the
invoicing team).

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=199684843

java/google/registry/flows/domain/DomainCreateFlow.java

@@ -525,6 +525,7 @@ public class DomainCreateFlow implements TransactionalFlow {
         .setReason(Reason.FEE_EARLY_ACCESS)
         .setTargetId(createBillingEvent.getTargetId())
         .setClientId(createBillingEvent.getClientId())
+        .setPeriodYears(1)
         .setCost(feesAndCredits.getEapCost())
         .setEventTime(createBillingEvent.getEventTime())
         .setBillingTime(createBillingEvent.getBillingTime())