Added check for documented reserved SD-ID's

Author: bbergquist0930

src/main/java/com/cloudbees/syslog/SDElement.java

@@ -30,6 +30,16 @@ public class SDElement implements Serializable {
 
     private static final long serialVersionUID = 1L;
 
+    /**
+     * Reserved SD-IDs as documented in <a href="https://www.rfc-editor.org/rfc/rfc5424.txt">RFC-5424</a>
+     */
+    public static final String[] RESERVED_SDID = new String[]{
+        "timeQuality",
+        "tzKnown",
+        "isSynced",
+        "syncAccuracy"
+    };
+
     public SDElement(String sdID) {
         validateSDID(sdID);
         this.sdID = sdID;
@@ -131,6 +141,18 @@ private void validateSDID(String sdName) {
         if (sdName.contains("\"")) {
             throw new IllegalArgumentException("SD-ID cannot contain '\"'");
         }
+        if (! sdName.contains("@")) {
+            boolean found = false;
+            for (String rn : RESERVED_SDID) {
+                if (rn.equals(sdName)) {
+                    found = true;
+                    break;
+                }
+            }
+            if (! found) {
+                throw new IllegalArgumentException("SD-ID is not known registered SDID: " + sdName);
+            }
+        }
     }
 
 }

src/test/java/com/cloudbees/syslog/SyslogMessageTest.java

@@ -87,7 +87,6 @@ public void testRfc5424FormatWithStructuredData() throws Exception {
         expected = "<14>1 2013-12-05T10:30:05.000Z myserver.example.com my_app - - [exampleSDID@32473 iut=\"3\" eventSource=\"Application\" eventID=\"1011\"][examplePriority@32473 class=\"high\"] a syslog message";
 
         assertThat(actual, is(expected));
-        
     }
 
     @Test