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/session/HelloFlow.java

@@ -18,8 +18,13 @@ import google.registry.flows.Flow;
 import google.registry.model.eppoutput.EppOutput;
 import google.registry.model.eppoutput.Greeting;
 
+import javax.inject.Inject;
+
 /** A flow for an Epp "hello". */
 public class HelloFlow extends Flow {
+
+  @Inject HelloFlow() {}
+
   @Override
   public EppOutput run() {
     return EppOutput.create(Greeting.create(now));

java/google/registry/flows/session/LoginFlow.java

@@ -41,6 +41,8 @@ import google.registry.util.FormattingLogger;
 
 import java.util.Set;
 
+import javax.inject.Inject;
+
 /**
  * An EPP flow for login.
  *
@@ -68,6 +70,8 @@ public class LoginFlow extends Flow {
   /** Maximum number of failed login attempts allowed per connection. */
   private static final int MAX_FAILED_LOGIN_ATTEMPTS_PER_CONNECTION = 3;
 
+  @Inject LoginFlow() {}
+
   /** Run the flow and log errors. */
   @Override
   public final EppOutput run() throws EppException {

java/google/registry/flows/session/LogoutFlow.java

@@ -20,12 +20,17 @@ import google.registry.flows.EppException;
 import google.registry.flows.LoggedInFlow;
 import google.registry.model.eppoutput.EppOutput;
 
+import javax.inject.Inject;
+
 /**
  * An EPP flow for logout.
  *
  * @error {@link google.registry.flows.LoggedInFlow.NotLoggedInException}
  */
 public class LogoutFlow extends LoggedInFlow {
+
+  @Inject LogoutFlow() {}
+
   @Override
   public final EppOutput run() throws EppException {
     sessionMetadata.invalidate();