Dagger, meet Flows. Flows, meet Dagger.

Daggerizes all of the EPP flows. This does not change anything yet
about the flows themselves, just how they are invoked, but after
this CL it's safe to @Inject things into flow classes.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=125382478

java/google/registry/flows/host/HostCreateFlow.java

@@ -40,6 +40,8 @@ import google.registry.model.host.HostResource.Builder;
 import google.registry.model.ofy.ObjectifyService;
 import google.registry.model.reporting.HistoryEntry;
 
+import javax.inject.Inject;
+
 /**
  * An EPP flow that creates a new host resource.
  *
@@ -67,6 +69,8 @@ public class HostCreateFlow extends ResourceCreateFlow<HostResource, Builder, Cr
    */
   private Optional<Ref<DomainResource>> superordinateDomain;
 
+  @Inject HostCreateFlow() {}
+
   @Override
   protected void initResourceCreateOrMutateFlow() throws EppException {
     superordinateDomain = Optional.fromNullable(lookupSuperordinateDomain(