Fix bug in rule serialization for transform match/replace

Author: pimterry

src/model/rules/definitions/http-rule-definitions.ts

@@ -228,6 +228,14 @@ serializr.createModelSchema(TransformingHandler, {
             updateHeaders: serializeWithUndefineds,
             updateJsonBody: serializeWithUndefineds,
             replaceBody: serializeBuffer,
+            matchReplaceBody: serializr.list(
+                serializr.custom(
+                    ([key, value]: [RegExp, string]) =>
+                        [{ source: key.source, flags: key.flags }, value],
+                    ([key, value]: [{ source: string, flags: string }, string]) =>
+                        [new RegExp(key.source, key.flags), value]
+                )
+            ),
             '*': Object.assign(serializr.raw(), { pattern: { test: () => true } })
         })
     )