Explaining the caveats in writing to the same key with a workaround example

[ilianiliev-redis]

Explaining the caveats in writing to the same key with a workaround example

Ticket: https://redislabs.atlassian.net/browse/RDSC-5181

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Note

Low Risk
Documentation-only change adding guidance for a known edge case (shared-key deletes) and an example workaround; no runtime behavior is modified.

Overview
Adds a new caveat to data-denormalization.md that when multiple RDI jobs write to the same Redis key, a delete event from any source entity can remove the shared key, and links to a workaround.

Introduces a new transform example doc, redis-write-same-key.md, showing how to use row_format: full, convert delete opcode events into updates, and null out fields so jobs can safely on_update: merge into a shared Redis JSON document without deleting the key.

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[andy-stark-redis]

Couple of suggestions, but otherwise LGTM.

[andy-stark-redis]

Suggested change

	# If you have overlapping field names e.g. FK and PK have the same name, or both table have
	# a field called "id" and may want to remove the field from the after object to prevent it
	# from overwriting the PK.
	# If you have overlapping field names (for example, FK and PK have the same name, or both tables have
	# a field called "id"), you may want to remove the field from the after object to prevent it
	# from overwriting the PK.

[andy-stark-redis]

Suggested change

	In the case of using the same key for different jobs, deleting any of the entities will result in the key being remove from the target.
	If you are using the same key for different jobs, deleting any of the entities will result in the key being removed from the target.