[BUG][JAVA][RestTemplate] Specified Accept header values generates uncompilable code

Created by: crosbyb

Description

openapi-generator version

4.1.0, 4.1.3

OpenAPI declaration file content or url

See the attached swagger contract for the full example.

        "parameters": [
          {
            "in": "header",
            "name": "Accept",
            "schema": {
              "enum": [
                "application/vnd.geo+json",
                "text/csv"
              ]
            },
            "required": true
          }
        ],

Command line used for generation

swagger-client-config.json:

{
  "modelPackage": "sc.v0.client.model",
  "apiPackage": "svc.v0.client",
  "library": "resttemplate",
  "groupId": "api.clients",
  "artifactId": "svc-client",
  "artifactVersion": "0.0.1"
}

java -jar ./codegen.jar generate -c ./swagger-client-config.json -i ./swagger.json -g java -o client/

Steps to reproduce

mkdir client
java -jar ./codegen.jar generate -c ./swagger-client-config.json  -i ./swagger.json -g java -o client/
cd client/ && mvn install  -q -Dmaven.test.skip=true -Dmaven.javadoc.skip=true && cd ..

You'll see the following error when Maven tries to compile:

[ERROR] /Users/brad/tmp/openapi-accept/client/src/main/java/svc/v0/client/ServiceApi.java:[77,31] variable accept is already defined in method getAllThings(java.lang.String)

There is already a local variable in the method named accept, so adding the accept header as an argument to the method creates the conflict.