Extract out contruction of Web Key Directory URLs

Moves `toWebKeyDirectoryURL` to a separate class adding unit tests
for URL correctness as well as support for spaces at the beginning
and end of the e-mail. Spaces are frequently automatically inserted
by soft keyboards.

OpenKeychain/src/test/java/org/sufficientlysecure/keychain/util/WebKeyDirectoryUtilTest.java

@@ -0,0 +1,30 @@
+package org.sufficientlysecure.keychain.util;
+
+import org.junit.Test;
+
+import java.net.URL;
+
+import static junit.framework.Assert.assertEquals;
+import static junit.framework.Assert.assertNotNull;
+
+public class WebKeyDirectoryUtilTest {
+
+    @Test
+    public void testWkd() {
+        URL url = WebKeyDirectoryUtil.toWebKeyDirectoryURL("test-wkd@openkeychain.org");
+        assertNotNull(url);
+        assertEquals("openkeychain.org", url.getHost());
+        assertEquals("https", url.getProtocol());
+        assertEquals("/.well-known/openpgpkey/hu/4hg7tescnttreaouu4z1izeuuyibwww1", url.getPath());
+    }
+
+    @Test
+    public void testWkdWithSpaces() {
+        URL url = WebKeyDirectoryUtil.toWebKeyDirectoryURL(" test-wkd@openkeychain.org ");
+        assertNotNull(url);
+        assertEquals("openkeychain.org", url.getHost());
+        assertEquals("https", url.getProtocol());
+        assertEquals("/.well-known/openpgpkey/hu/4hg7tescnttreaouu4z1izeuuyibwww1", url.getPath());
+    }
+
+}