Provide utf-characters instead of escape strings.

Also adapt tests to check the new functionality.
Implements task-25740.

CHANGELOG.md

+# Changes in version 6.0-1.13.0 - 2018-04-??
+
+ * Minor changes
+   - Turn valid utf-8 escape sequences into utf-8 characters.
+
+
 # Changes in version 5.2-1.12.0 - 2018-04-06
 
  * Medium changes

src/main/java/org/torproject/onionoo/util/FormattingUtils.java

@@ -3,6 +3,8 @@
 
 package org.torproject.onionoo.util;
 
+import static org.apache.commons.lang3.StringEscapeUtils.unescapeJava;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -58,8 +60,8 @@ public class FormattingUtils {
       StringBuffer sb = new StringBuffer();
       Matcher mat = escapePattern.matcher(text);
       while (mat.find()) {
-        String unescaped = mat.group(1);
-        mat.appendReplacement(sb, unescaped);
+        String unescaped = mat.group(1).substring(1);
+        mat.appendReplacement(sb, unescapeJava(unescaped));
       }
       mat.appendTail(sb);
       return sb.toString();

src/test/resources/lines-for-escape-tests.txt

@@ -2,15 +2,21 @@
 
 abc
 abc
-\\\\u
-\\\\u
+\\\\u00bb \\\\u \\\\u00ab
+» \\\\u «
 Haha/\\\\@/\\\\live/\\\\./\\\\co/\\\\./\\\uk
 Haha/\\\\@/\\\\live/\\\\./\\\\co/\\\\./\\\uk
-\\\\u20ac
-\\u20ac
-\\\\u0024
-\\u0024
-some \\\\u20ac other string \\\\u0024 to unescape
-some \\u20ac other string \\u0024 to unescape
-abcd efg\\\\u0024xyz\\\\uxxxx
-abcd efg\\u0024xyz\\\\uxxxx
+Euro \\\\u20ac
+Euro €
+Dollar \\\\u0024
+Dollar $
+Pound \\\\u00a3
+Pound £
+Yen \\\\u00a5
+Yen ¥
+\\\\u00a1some \\\\u00dE other string \\\\u00e7 to unescape!
+¡some Þ other string ç to unescape!
+abcd efg cent \\\\u00a2xyz\\\\uxxxx
+abcd efg cent ¢xyz\\\\uxxxx
+Telef\\\\u00F4nica
+Telefônica