[BUG] [JAVA] [openapi-yaml] [spring] wrong generated example text

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• 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

direct usage of allOf destroyes the example of a property with type object without further properties.

expected output (with v7.4.0)

yaml

            example:
              someMeaningfulNumber: 25009779801

java

String exampleString = "{ \"data\" : { \"someMeaningfulNumber\" : 25009779801 }, \"someProperty\" : \"someProperty\" }";

failing output (>7.4.0)

yaml

      example:
        data: "{\"someMeaningfulNumber\":25009779801}"

java

String exampleString = "{ \"data\" : \"{\\"someMeaningfulNumber\\":25009779801}\", \"someProperty\" : \"someProperty\" }";

the generated yaml can't be used for further generation. the generated java code doesn't compile.

openapi-generator version

7.4.0 -> OK
7.5.0 -> fail
7.6.0 -> fail
7.7.0 -> fail

OpenAPI declaration file content or url

https://github.com/kingofdisasterr/openapi-generator-example/blob/main/src/main/resources/yaml/someinterface.yaml

full project:
https://github.com/kingofdisasterr/openapi-generator-example

Generation Details

mvn clean verifyof https://github.com/kingofdisasterr/openapi-generator-example/blob/main/pom.xml

Start with the linked someinterface.yaml and run mvn clean verify in the reproduction project, comparing generation with OpenAPI Generator 7.4.0 and later versions. Trace the generated YAML and Java example output to identify where the object example becomes a string. Done means the YAML preserves the object example and the generated Java example compiles as expected.