Relax limit on max string size (elastic#96031)

Jackson 2.15 introduced a (rough) maximum limit on string length. This
commit relaxes that limit to its maximum size, leaving document size
constraints to other existing limits in the system. We can revisit
whether string length within a document should be independently
constrainted later.

Author: rjernst

libs/x-content/impl/src/main/java/org/elasticsearch/xcontent/provider/json/JsonXContentImpl.java

@@ -10,8 +10,10 @@
 
 import com.fasterxml.jackson.core.JsonEncoding;
 import com.fasterxml.jackson.core.JsonFactory;
+import com.fasterxml.jackson.core.JsonFactoryBuilder;
 import com.fasterxml.jackson.core.JsonGenerator;
 import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.StreamReadConstraints;
 
 import org.elasticsearch.xcontent.XContent;
 import org.elasticsearch.xcontent.XContentBuilder;
@@ -44,7 +46,12 @@ public static final XContent jsonXContent() {
     }
 
     static {
-        jsonFactory = new JsonFactory();
+        var builder = new JsonFactoryBuilder();
+        // jackson 2.15 introduced a max string length. We have other limits in place to constrain max doc size,
+        // so here we set to max value (2GiB) so as not to constrain further than those existing limits.
+        builder.streamReadConstraints(StreamReadConstraints.builder().maxStringLength(Integer.MAX_VALUE).build());
+
+        jsonFactory = builder.build();
         jsonFactory.configure(JsonGenerator.Feature.QUOTE_FIELD_NAMES, true);
         jsonFactory.configure(JsonParser.Feature.ALLOW_COMMENTS, true);
         jsonFactory.configure(JsonFactory.Feature.FAIL_ON_SYMBOL_HASH_OVERFLOW, false); // this trips on many mappings now...