Ruby: add getAValueReachingRhs

ruby/ql/lib/codeql/ruby/ApiGraphs.qll

@@ -48,6 +48,11 @@ module API {
      */
     DataFlow::Node getARhs() { Impl::def(this, result) }
 
+    /**
+     * Gets a data-flow node that may interprocedurally flow to the value escaping into this API component.
+     */
+    DataFlow::Node getAValueReachingRhs() { result = Impl::trackDefNode(this.getARhs()) }
+
     /**
      * Gets a call to a method on the receiver represented by this API component.
      */