[C-libcurl] Support setting basePath and apiKeys when creating an apiClient

Created by: ityuhui

After generating a C client, user will use apiClient_create to create an apiClient to execute REST request operation.

But for now, apiClient_create does not accept any parameter so apiClient cannot get any user setting. e.g.

apiClient_t *apiClient_create() {
    curl_global_init(CURL_GLOBAL_ALL);
    apiClient_t *apiClient = malloc(sizeof(apiClient_t));
    apiClient->basePath = "http://localhost";
    apiClient->dataReceived = NULL;
    apiClient->response_code = 0;
    apiClient->apiKeys = NULL;

    return apiClient;
}

I updated the template code, let the apiClient_create can get user settings:

apiClient_t *apiClient_create(const char *basePath
, list_t *apiKeys
) {
    curl_global_init(CURL_GLOBAL_ALL);
    apiClient_t *apiClient = malloc(sizeof(apiClient_t));
    if(basePath){
        apiClient->basePath = strdup(basePath);
    }else{
        apiClient->basePath = strdup("http://localhost");
    }
    apiClient->dataReceived = NULL;
    apiClient->response_code = 0;
    apiClient->apiKeys = apiKeys;

    return apiClient;
}

I also updated the header file and apiClient_free.

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• If contributing template-only or documentation-only changes which will change sample output, build the project before.
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