Workflow API Error Handling

Summary

A lightweight result type and one translator provide the main API error pattern.

Validation failures become bad-request results with a message object.
Missing resources become not-found results with a message object.
State/duplicate/key conflicts become conflict results with a message object.
Successful results become standard success or endpoint-selected created results.

Definition and instance detail handlers create their own message-shaped not-found responses.

A middleware catches tenant-related invalid-operation exceptions, writes a bad-request status and serializes a message object.

Route mismatch, binding errors and unhandled exceptions do not have a Workflow-specific error contract in reviewed source.

No problem-details standard, error code, validation field map, global exception handler or persistence-exception translation exists.

Public error schema, correlation exposure, logging of failures and persistence error normalization require confirmation.

Workflow API, approval endpoint, Workflow Service.