C#: Re-factor ExponentialRegexDataFlow to use the new API.

Author: michaelnebel

csharp/ql/lib/semmle/code/csharp/security/dataflow/ReDoSQuery.qll

@@ -78,26 +78,40 @@ predicate isExponentialRegex(StringLiteral s) {
 }
 
 /**
+ * DEPRECATED: Use `ExponentialRegexDataflow` instead.
+ *
  * A data flow configuration for tracking exponential worst case time regular expression string
  * literals to the pattern argument of a regex.
  */
-class ExponentialRegexDataflow extends DataFlow2::Configuration {
+deprecated class ExponentialRegexDataflow extends DataFlow2::Configuration {
   ExponentialRegexDataflow() { this = "ExponentialRegex" }
 
   override predicate isSource(DataFlow::Node s) { isExponentialRegex(s.asExpr()) }
 
   override predicate isSink(DataFlow::Node s) { s.asExpr() = any(RegexOperation c).getPattern() }
 }
 
+/**
+ * A data flow configuration for tracking exponential worst case time regular expression string
+ * literals to the pattern argument of a regex.
+ */
+private module ExponentialRegexDataFlowConfig implements DataFlow::ConfigSig {
+  predicate isSource(DataFlow::Node s) { isExponentialRegex(s.asExpr()) }
+
+  predicate isSink(DataFlow::Node s) { s.asExpr() = any(RegexOperation c).getPattern() }
+}
+
+module ExponentialRegexDataFlow = DataFlow::Global<ExponentialRegexDataFlowConfig>;
+
 /**
  * An expression passed as the `input` to a call to a `Regex` method, where the regex appears to
  * have exponential behavior.
  */
 class ExponentialRegexSink extends DataFlow::ExprNode, Sink {
   ExponentialRegexSink() {
-    exists(ExponentialRegexDataflow regexDataflow, RegexOperation regexOperation |
+    exists(RegexOperation regexOperation |
       // Exponential regex flows to the pattern argument
-      regexDataflow.hasFlow(_, DataFlow::exprNode(regexOperation.getPattern()))
+      ExponentialRegexDataFlow::flow(_, DataFlow::exprNode(regexOperation.getPattern()))
     |
       // This is used as an input for this pattern
       this.getExpr() = regexOperation.getInput() and