Fix JacksonEvent delete for fields with slashes in field names

[jkbedi]

Description

This change fixes a bug in JacksonEvent.delete() where fields containing forward slashes in their names could not be properly deleted when using JSON Pointer escaped keys.

Problem: When attempting to delete a field like {"A/B": "allow"} using the JSON Pointer escaped key "A~1B", the deletion would fail because ObjectNode.remove() was looking for a field literally named "A~1B" instead of the actual field name "A/B".

Solution: Modified the delete method to unescape JSON Pointer field names by converting ~1 back to / before calling ObjectNode.remove(). This allows the ObjectNode to find and remove the correct field.

Testing: Added testDelete_withSlashInFieldName_jsonPointerEscaping() test that verifies fields with forward slashes in their names can be successfully deleted using JSON Pointer escaped keys.

Issues Resolved

Resolves #5953

Check List

• [Y ] New functionality includes testing.
• New functionality has a documentation issue. Please link to it in this PR.
• New functionality has javadoc added
• Commits are signed with a real name per the DCO

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[kkondaka]

Is this issue only with leafkey? What if the key is "A/B/C/D" where "B/C" is a single key inside A and with child D?

[dlvenable]

Yes, I also wonder if this is general enough.

Relatedly, this is in the delete() call. Is this not a problem for put and get as well? And it would be better to fix this in the EventKey would result in better performance as well because you won't need to call String::replace for every delete operation.

[dlvenable]

@jkbedi , Thank you for the contribution. We have a few questions about the implementation.

Also, your DCO is failing. Please see:

https://github.com/opensearch-project/data-prepper/blob/main/CONTRIBUTING.md

And you will need to rebase your commits so that all have the DCO Sign-Off.