Use same resource instance for operation processing and generating ID trees

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Feature request

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Description

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Features:

In previous versions, a single resource instance was used for performing the operation and generating the response. Now these parts of the request handling are split into distinct steps which each use their own resource instances. As a result, any instance variables stored on the resource during the operation are not present when generating the response.

Any resource instances that are created for the operation processing should be used for the response generation as well.

No files or tests are named. Start by tracing the request-handling paths for operation processing and response generation, then compare where resource instances are created. Done means the resource instances used during operations are also used to generate responses, preserving operation-time instance variables.