Expose metadata via dedicated class for scripting index and update contexts #86472
Description
Currently, scripts access metadata such as by various keys on the context object. Changing this to getters and setters on a metadata object will separate the document source from the metadata and allow better compile time checking for accidentally misspelled keys.
| Index API | Update API | Update by query API | Reindex API | |
|---|---|---|---|---|
| _index | W | R | R | W |
| _id | R | R | R | W |
| _routing | R | R | R | W |
| _version | R | R | R | W |
| _version_type | R | |||
| timestamp | R | |||
| now | R | |||
| op | W | W | W |