Duplicated header values when an endpoint can be called with different headers

[didjoman]

Describe the bug

If a controller has an endpoint that can be called with different possible headers (key + value), then in the doc generated, in the parameters, the possible values for the headers appear twice.

How to reproduce

(Using Java 11, SpringBoot 2.7.2, springdoc-openapi-webmvc-core 1.6.10 based on Swagger-core 2.2.2)
git clone https://github.com/didjoman/springdoc-double-headers-issue
Run the application (spring boot).
Run curl --location --request GET 'http://localhost:8080/doc' --header 'Content-Type: application/json'

Expected behavior

We should obtain a schema like this, without duplication of the enum values of the parameters.

{
    "openapi": "3.0.1",
    "info": {
        "title": "OpenAPI definition",
        "version": "v0"
    },
    "servers": [
        {
            "url": "http://localh",
            "description": "Generated server url"
        }
    ],
    "paths": {
        "/": {
            "get": {
                "tags": [
                    "basic-controller"
                ],
                "operationId": "get1_1_1",
                "parameters": [
                    {
                        "name": "foo",
                        "in": "header",
                        "schema": {
                            "type": "string",
                            "enum": [
                                "bar"
                            ]
                        }
                    },
                    {
                        "name": "fi",
                        "in": "header",
                        "schema": {
                            "type": "string",
                            "enum": [
                                "ri"
                            ]
                        }
                    },
                    {
                        "name": "User-Agent",
                        "in": "header",
                        "schema": {
                            "type": "string",
                            "enum": [
                                "MyUserAgent"
                            ]
                        }
                    }
                ],
                "responses": {
                    "200": {
                        "description": "OK",
                        "content": {
                            "*/*": {
                                "schema": {
                                    "type": "string"
                                }
                            }
                        }
                    }
                }
            }
        }
    },
    "components": {}
}

Actual behavior

Today, the possible values of the headers other than the first one get duplicated.

{
    "openapi": "3.0.1",
    "info": {
        "title": "OpenAPI definition",
        "version": "v0"
    },
    "servers": [
        {
            "url": "http://localh",
            "description": "Generated server url"
        }
    ],
    "paths": {
        "/": {
            "get": {
                "tags": [
                    "basic-controller"
                ],
                "operationId": "get1_1_1",
                "parameters": [
                    {
                        "name": "foo",
                        "in": "header",
                        "schema": {
                            "type": "string",
                            "enum": [
                                "bar"
                            ]
                        }
                    },
                    {
                        "name": "fi",
                        "in": "header",
                        "schema": {
                            "type": "string",
                            "enum": [
                                "ri",
                                "ri"
                            ]
                        }
                    },
                    {
                        "name": "User-Agent",
                        "in": "header",
                        "schema": {
                            "type": "string",
                            "enum": [
                                "MyUserAgent",
                                "MyUserAgent"
                            ]
                        }
                    }
                ],
                "responses": {
                    "200": {
                        "description": "OK",
                        "content": {
                            "*/*": {
                                "schema": {
                                    "type": "string"
                                }
                            }
                        }
                    }
                }
            }
        }
    },
    "components": {}
}

Additional context

/