Blog Client with Factory and Validator

This implements a simple initial blog client that covers the basic blog
actions, but no deletion/removal of blogs, yet.

Classes for Blogs and Blog Post Headers have been introduced along with
the associated factories.

A `BlogPostValidator` has been added that validates incoming blog posts.

Closes #402
Closes #404

briar-core/src/org/briarproject/identity/IdentityManagerImpl.java

 package org.briarproject.identity;
 
+import org.briarproject.api.contact.Contact;
 import org.briarproject.api.db.DatabaseComponent;
 import org.briarproject.api.db.DbException;
 import org.briarproject.api.db.Transaction;
+import org.briarproject.api.identity.Author.Status;
 import org.briarproject.api.identity.AuthorId;
 import org.briarproject.api.identity.IdentityManager;
 import org.briarproject.api.identity.LocalAuthor;
 
 import java.util.Collection;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 import java.util.concurrent.CopyOnWriteArrayList;
 
 import javax.inject.Inject;
 
+import static org.briarproject.api.identity.Author.Status.UNKNOWN;
+import static org.briarproject.api.identity.Author.Status.VERIFIED;
+
 class IdentityManagerImpl implements IdentityManager {
 	private final DatabaseComponent db;
 	private final List<AddIdentityHook> addHooks;
@@ -87,4 +94,22 @@ class IdentityManagerImpl implements IdentityManager {
 			db.endTransaction(txn);
 		}
 	}
+
+	@Override
+	public Status getAuthorStatus(AuthorId authorId) throws DbException {
+		Transaction txn = db.startTransaction(false);
+		try {
+			// Compare to the IDs of the user's identities
+			for (LocalAuthor a : db.getLocalAuthors(txn))
+				if (a.getId().equals(authorId)) return VERIFIED;
+			// Compare to the IDs of contacts' identities
+			for (Contact c : db.getContacts(txn))
+				if (c.getAuthor().getId().equals(authorId)) return VERIFIED;
+
+			// TODO also handle UNVERIFIED when #261 is implemented
+			return UNKNOWN;
+		} finally {
+			db.endTransaction(txn);
+		}
+	}
 }