[BUG][java-helidon-server] If a service only contains a single endpoint, the routing is wrong

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

When generating a service with only a single endpoint, the "/" path pattern is used. Actual output:

    @Override
    public void routing(HttpRules rules) {
        rules.get("/", this::filedownload);
    }

However this means that the actual endpoint is not found, and even if it were, the path parameter can not be extracted.
Expected output would be.

    @Override
    public void routing(HttpRules rules) {
        rules.get("/bugs/filedownload/{fileName}", this::filedownload);
    }

openapi-generator version

7.8.0 gradle plugin

OpenAPI declaration file content or url

bugs.json

Generation Details

openApiGenerate {
    generatorName.set("java-helidon-server")
    inputSpecRootDirectory.set("$rootDir/specs/")
    outputDir.set("$rootDir/src")
    apiPackage.set("my.package.api")
    modelPackage.set("my.package.model")
    invokerPackage.set("my.package.api.services")
    validateSpec.set(true)
    generateApiTests.set(false)
    configOptions.set([
            apiPackage          : "my.package.services",
            modelPackage        : "my.package.model",
            invokerPackage        : "my.package.services",
            dateLibrary         : "java8",
            gradleProject       : "true",
            groupId             : "my.package",
            artifactId          : "example",
            library             : "se",
            helidonVersion      : "$helidonVersion",
            serializationLibrary: "jackson",
            fullProject         : "false",
            useAbstractClass    : "true",
            "x-helidon-groupBy" : "first-path-segment"
    ])
}

Steps to reproduce

Use the java-helidon-server plugin to generate the server implementation

Start with the bugs.json OpenAPI declaration and reproduce generation using the java-helidon-server plugin configuration from the report. Inspect the generated routing for a service with one endpoint; done means it uses the endpoint path "/bugs/filedownload/{fileName}" instead of "/" and preserves path-parameter extraction.