One-off request context on behalf of a user

Enable the invocation of Gerrit API on behalf of another user.

Example use with a ChangeApi invocation:

  try (ManualRequestContext ctx = oneOffRequestContext.openAs(userId)) {
    ChangeApi cApi = gApi.changes().id(change.getId().get());
    ...
  }

Change-Id: I48c292b24613bc32406bf1673a11430267a21d67

gerrit-server/src/main/java/com/google/gerrit/server/util/OneOffRequestContext.java

@@ -14,7 +14,9 @@
 
 package com.google.gerrit.server.util;
 
+import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.InternalUser;
 import com.google.gwtorm.server.OrmException;
 import com.google.gwtorm.server.SchemaFactory;
@@ -27,25 +29,34 @@ import com.google.inject.Singleton;
  * Each call to {@link #open()} opens a new {@link ReviewDb}, so this class
  * should only be used in a bounded try/finally block.
  * <p>
- * The user in the request context is {@link InternalUser}.
+ * The user in the request context is {@link InternalUser} or the
+ * {@link IdentifiedUser} associated to the userId passed as parameter.
  */
 @Singleton
 public class OneOffRequestContext {
   private final InternalUser.Factory userFactory;
   private final SchemaFactory<ReviewDb> schemaFactory;
   private final ThreadLocalRequestContext requestContext;
+  private final IdentifiedUser.GenericFactory identifiedUserFactory;
 
   @Inject
   OneOffRequestContext(InternalUser.Factory userFactory,
       SchemaFactory<ReviewDb> schemaFactory,
-      ThreadLocalRequestContext requestContext) {
+      ThreadLocalRequestContext requestContext,
+      IdentifiedUser.GenericFactory identifiedUserFactory) {
     this.userFactory = userFactory;
     this.schemaFactory = schemaFactory;
     this.requestContext = requestContext;
+    this.identifiedUserFactory = identifiedUserFactory;
   }
 
   public ManualRequestContext open() throws OrmException {
     return new ManualRequestContext(userFactory.create(),
         schemaFactory, requestContext);
   }
+
+  public ManualRequestContext openAs(Account.Id userId) throws OrmException {
+    return new ManualRequestContext(identifiedUserFactory.create(userId),
+        schemaFactory, requestContext);
+  }
 }