Handles matrix attribute definitions only - for simple definitions use POST /catalogs/nodes/{id}/attributes/{attributeDefinitionId} - and fails when the category already has this
attribute definition as a CLA; change the existing values with PUT /catalogs/nodes/{id}/attributes/{attributeDefinitionId}/matrix instead. An attribute inherited from a parent
category does not count as assigned here, so the call succeeds and creates an assignment on this category that
overrides the inherited one.

The attribute is stored on the category immediately, while copying its values onto products runs as a background
task. That task covers the products in this category; the products in its sub-categories are reached only once
propagation is switched on for this attribute, which is off on a newly created CLA - switch it on, as well as
mandatory, with PATCH /catalogs/nodes/{id}/attributes/{attributeDefinitionId}; the lock flag is not supported
for matrix definitions. The task ID is returned in the Resource-Id response header and Location points at
GET /async/status/{taskId}, which reports whether the propagation has finished.

A request body is always required, including when the attribute is attached with no values set - send
{"matrix": {}} in that case. The keys inside matrix are the column value IDs and, one level deeper, the
row value IDs taken from the definition's restriction, read with GET /definitions/{attributeDefinitionId};
column and row names are rejected.

For more detailed information on how to work with Category Level Attributes in Bluestone PIM, refer to our help
pages Category Level Attributes (CLA).