fixes networknt#1912 Add a DummyDecryptor for testing (networknt#1913)

decryptor/src/main/java/com/networknt/decrypt/DummyDecryptor.java

@@ -0,0 +1,24 @@
+package com.networknt.decrypt;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class DummyDecryptor implements Decryptor {
+    private static final Logger logger = LoggerFactory.getLogger(DummyDecryptor.class);
+    public DummyDecryptor() {
+        if(logger.isInfoEnabled()) logger.info("DummyDecryptor is constructed.");
+    }
+
+    public String decrypt(String input) {
+        if (!input.startsWith(CRYPT_PREFIX)) {
+            logger.error("The secret text is not started with prefix " + CRYPT_PREFIX);
+            throw new RuntimeException("Unable to decrypt, input string does not start with 'CRYPT'.");
+        }
+        String[] parts = input.split(":");
+        if(parts.length != 2) {
+            logger.error("The secret text is not formatted correctly with CRYPT:text");
+            throw new RuntimeException("Unable to decrypt, input string is not formatted correctly with CRYPT:text");
+        }
+        return parts[1];
+    }
+}