Allow MaD sanitizers for java/server-side-template-injection

Author: owen-mc

java/ql/lib/semmle/code/java/security/TemplateInjection.qll

@@ -46,3 +46,7 @@ private class DefaultTemplateInjectionSink extends TemplateInjectionSink {
 
 private class DefaultTemplateInjectionSanitizer extends TemplateInjectionSanitizer instanceof SimpleTypeSanitizer
 { }
+
+private class ExternalTemplateInjectionSanitizer extends TemplateInjectionSanitizer {
+  ExternalTemplateInjectionSanitizer() { barrierNode(this, "template-injection") }
+}