GUACAMOLE-641: Read token/secret mapping from YAML instead of JSON.

extensions/guacamole-vault/modules/guacamole-vault-base/pom.xml

@@ -49,11 +49,15 @@
             <scope>provided</scope>
         </dependency>
 
-        <!-- Jackson for JSON support -->
+        <!-- Jackson for YAML support -->
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>
         </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.dataformat</groupId>
+            <artifactId>jackson-dataformat-yaml</artifactId>
+        </dependency>
 
         <!-- Guice -->
         <dependency>