Avoid _expandIri event during @json type check.

- Add event filter to avoid reletive reference event while expanding to
  check if a value is `@json`.
- Update tests.
- Add safe/strict testing flags.

Author: davidlehn

lib/expand.js

@@ -527,7 +527,19 @@ async function _expandObject({
   const isJsonType = element[typeKey] &&
     _expandIri(activeCtx,
       (_isArray(element[typeKey]) ? element[typeKey][0] : element[typeKey]),
-      {vocab: true}, {...options, typeExpansion: true}) === '@json';
+      {vocab: true}, {
+        ...options,
+        typeExpansion: true,
+        eventHandler: [
+          // filter to avoid relative reference events
+          ({event, next}) => {
+            if(event.code !== 'relative IRI after expansion') {
+              next();
+            }
+          },
+          options.eventHandler
+        ]
+      }) === '@json';
 
   for(const key of keys) {
     let value = element[key];