[BUG] [SPRING] OpenAPI Generator generates enums that does not implement the interface for model with "OneOf" in the schema

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

openapi-generator version

7.1.0

OpenAPI declaration file content or url

      "DefaultPublicationType": {
        "type": "string",
        "enum": [
          "FLIGHT_DATA",
          "ARRIVAL_SEQUENCE_DATA",
          "AIRPORT_CONFIGURATION_DATA"
        ]
      },
      "OtherPublicationType": {
        "type": "string",
        "pattern": "^OTHER:[A-Z_][A-Z0-9_]*$"
      },
      "Publication": {
        "description": "A SWIM Publication identifies a topic together with its content type, formal content type definition, and supported filters.",
        "oneOf": [
          {
            "$ref": "#/components/schemas/DefaultPublicationType"
          },
          {
            "$ref": "#/components/schemas/OtherPublicationType"
          }
        ]
      },

Generation Details

@Generated(value = "org.openapitools.codegen.languages.SpringCodegen")
public interface Publication {
}

@Generated(value = "org.openapitools.codegen.languages.SpringCodegen")
public enum DefaultPublicationType {
  
  FLIGHT_DATA("FLIGHT_DATA"),
  
  ARRIVAL_SEQUENCE_DATA("ARRIVAL_SEQUENCE_DATA"),
  
  AIRPORT_CONFIGURATION_DATA("AIRPORT_CONFIGURATION_DATA");

  private String value;

  DefaultPublicationType(String value) {
    this.value = value;
  }

  @JsonValue
  public String getValue() {
    return value;
  }

  @Override
  public String toString() {
    return String.valueOf(value);
  }

  @JsonCreator
  public static DefaultPublicationType fromValue(String value) {
    for (DefaultPublicationType b : DefaultPublicationType.values()) {
      if (b.value.equals(value)) {
        return b;
      }
    }
    throw new IllegalArgumentException("Unexpected value '" + value + "'");
  }
}

Steps to reproduce

 <configuration>
                            <!-- see: https://openapi-generator.tech/docs/generators/spring/-->
                            <skipValidateSpec>true</skipValidateSpec>
                            <inputSpec>${project.basedir}/src/main/resources/openapi.json</inputSpec>
                            <generatorName>spring</generatorName>
                            <configOptions>
                                <useSpringBoot3>true</useSpringBoot3>
                                <useOneOfInterfaces>true</useOneOfInterfaces>
                                <useOptional>true</useOptional>
                                <annotationLibrary>swagger2</annotationLibrary>
                                <delegatePattern>true</delegatePattern>
                                <hideGenerationTimestamp>true</hideGenerationTimestamp>
                                <hateoas>true</hateoas>
                                <useBeanValidation>true</useBeanValidation>
                                <performBeanValidation>true</performBeanValidation>
                            </configOptions>
                        </configuration>

Related issues/PRs

#16672 #14807 #11715 #15

Suggest a fix

The generated enumeration should implement the interface.

Start with the Spring generator's useOneOfInterfaces option and reproduce the issue using the provided OpenAPI schemas and XML configuration. Compare the generated Publication interface with DefaultPublicationType; done means the generated enum implements the interface, with the existing related issues used for context.