refactor: improve logging on Factory download failure

[simonfernandes]

Description

• Fixes errors being swallowed when tracing was enabled. The catch block would never throw and so the code continued until it errored trying to read a non existent stream which caused the ambiguous ERR_INVALID_ARG_TYPE error.
• Improves the logging by including the error message from the factory.

Before:

[2026-07-23T12:02:59.395+01:00] ERROR - Failed to generate the requested file(s)
{"err":{"error":{"code":"ERR_INVALID_ARG_TYPE"},"message":"Could not download generated pdf/proposal"},"originalUrl":"/download/pdf/proposal/31754"

After:

[2026-07-28T17:19:27.448+01:00] ERROR - Factory service failed to generate pdf/proposal: Could not create readable stream
error: large object 628393 does not exist undefined
{"exception":{"name":"Error","message":"Factory service failed to generate pdf/proposal: Could not create readable stream \nerror: large object 628393 does not exist undefined",

Motivation and Context

We see this vague error occasionally in logs at STFC and it is useful for diagnosing problems.

How Has This Been Tested

Manual testing checking logs with tracing enabled and disabled.

Fixes

UserOfficeProject/issue-tracker#1636

Changes

• A new function throwFactoryError is introduced to handle Factory download failures. It provides more detailed error messages, including the download type and the exact error message from the Factory service.
• The error handling in callFactoryService function has been updated to use the new throwFactoryError function.
• The error logging in the Factory middleware has been enhanced to log the underlying error along with its message, providing more context for debugging.

Depends on

Tests included/Docs Updated?

• I have added tests to cover my changes.
• All relevant doc has been updated