Address schema parsing bug for `array` type if `items` is null or missing & handle custom response code

Addresses Issue: #28 (closed)

• Address schema parsing bug for array type if items is null or missing. Indexer fails instead of skipping over the attribute.

Here is example of such attribute:

"Wellbores": {
  "pattern": ".*U1A1NjA3MDM2Mzk5MzUy:.*",
  "description": "The Well ID reference.",
  "type": "array"
}

• Handle custom response code, as Indexer has few. Indexer throws exceptions otherwise.

indexer-core/src/main/java/org/opengroup/osdu/indexer/error/GlobalExceptionMapperCore.java

@@ -83,6 +83,12 @@ public class GlobalExceptionMapperCore extends ResponseEntityExceptionHandler {
             this.logger.warning(exceptionMsg, e);
         }
 
-        return new ResponseEntity<Object>(e.getError(), HttpStatus.resolve(e.getError().getCode()));
+        // Support for non standard HttpStatus Codes
+        HttpStatus httpStatus = HttpStatus.resolve(e.getError().getCode());
+        if (httpStatus == null) {
+            return ResponseEntity.status(e.getError().getCode()).body(e);
+        } else {
+            return new ResponseEntity<>(e.getError(), httpStatus);
+        }
     }
 }
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