[typescript-fetch] Remove undefined headers

Created by: LeComptoirDesPharmacies

Remove undefined values from headers

I have encountered this issues when I want to pass an api key in the request but the endpoint support multiple header api key. So I use a fonction to set the right api key and set the other api key to undefined.

With this code :

function getFirstApiKey(keyName) {
    if (keyName === 'first-api-key') {
      return "my-key-value";
    }
    return undefined;
  };

The generated code for api key in the api endpoint :

    if (this.configuration && this.configuration.apiKey) {
        headerParameters["first-api-key"] = this.configuration.apiKey("first-api-key"); // first-api-key authentication
    }

    if (this.configuration && this.configuration.apiKey) {
        headerParameters["second-api-key"] = this.configuration.apiKey("second-api-key"); // second-api-key authentication
    }

The generated apiKey function :

    get apiKey(): ((name: string) => string) | undefined {
        const apiKey = this.configuration.apiKey;
        if (apiKey) {
            return typeof apiKey === 'function' ? apiKey : () => apiKey;
        }
        return undefined;
    }

Result headers :

first-api-key: my-key-value
second-api-key: undefined

Expected headers :

first-api-key: my-key-value

The headers was send with the two api key with one with the right value and the other with undefined as a string

To fix this issues, just remove any header who has undefined as value.

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Thanks for the review