Flatten the domain info flows

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=133955573

java/google/registry/flows/FlowModule.java

@@ -15,6 +15,7 @@
 package google.registry.flows;
 
 import static com.google.common.base.Preconditions.checkState;
+import static com.google.common.base.Strings.nullToEmpty;
 
 import com.google.common.base.Optional;
 import com.google.common.base.Strings;
@@ -22,6 +23,7 @@ import dagger.Module;
 import dagger.Provides;
 import google.registry.flows.exceptions.OnlyToolCanPassMetadataException;
 import google.registry.flows.picker.FlowPicker;
+import google.registry.model.domain.launch.ApplicationIdTargetExtension;
 import google.registry.model.domain.metadata.MetadataExtension;
 import google.registry.model.eppcommon.AuthInfo;
 import google.registry.model.eppcommon.Trid;
@@ -194,6 +196,15 @@ public class FlowModule {
     return ((SingleResourceCommand) resourceCommand).getTargetId();
   }
 
+  @Provides
+  @FlowScope
+  @ApplicationId
+  static String provideApplicationId(EppInput eppInput) {
+    // Treat a missing application id as empty so we can always inject a non-null value.
+    return nullToEmpty(
+        eppInput.getSingleExtension(ApplicationIdTargetExtension.class).getApplicationId());
+  }
+
   @Provides
   @FlowScope
   @PollMessageId
@@ -254,6 +265,11 @@ public class FlowModule {
   @Documented
   public @interface TargetId {}
 
+  /** Dagger qualifier for the application id for domain application flows. */
+  @Qualifier
+  @Documented
+  public @interface ApplicationId {}
+
   /** Dagger qualifier for the message id for poll flows. */
   @Qualifier
   @Documented