[BUG] [typescript-fetch] generated API references undeclared function objectToJSON

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

With a schema that contains an object as a property, generation for typescript-fetch produces an invalid client that contains a reference to an undeclared function objectToJSON.

openapi-generator version

latest (via docker hub)

OpenAPI declaration file content or url

See reprex at https://github.com/luketudge/openapi-reprex

Generation Details

docker run --rm \
    -v "${PWD}:/local" \
    openapitools/openapi-generator-cli generate \
    -i /local/openapi.json \
    -g typescript-fetch \
    -c /local/openapi_gen_config_typescript.json \
    -o /local/typescript

Steps to reproduce

https://github.com/luketudge/openapi-reprex

Related issues/PRs

Looks like a regression of #19280 but in a special case. Whereas the very similar bug reported there occurs for a schema in which the top-level item is declared as type 'object', the bug here is the same thing, but with a property that is declared as type object.

Suggest a fix

I'm looking into it. Not sure yet.

Start with the generation command and the openapi-reprex repository linked in the issue, using the typescript-fetch generator and its Docker invocation to reproduce the output. Trace where the generated client references objectToJSON and confirm that the generated client no longer contains an undeclared function reference for object-valued properties.