feat: support oauth token for explicitly cluster log on.

[nichozhan]

This is about Issue 21.

If I'm right, the details about how fabric choose credentials can be found in method io.fabric8.kubernetes.client.utils.HttpClientUtils#createApplicableInterceptors of kubernetes-client-5.12.2. A piece of its source code is below:

public static Map<String, io.fabric8.kubernetes.client.http.Interceptor> createApplicableInterceptors(Config config, HttpClient.Factory factory) {
    Map<String, io.fabric8.kubernetes.client.http.Interceptor> interceptors = new LinkedHashMap<>();
    
    // Header Interceptor
    interceptors.put(HEADER_INTERCEPTOR, new Interceptor() {
      
      @Override
      public void before(BasicBuilder builder, HttpHeaders headers) {
        if (Utils.isNotNullOrEmpty(config.getUsername()) && Utils.isNotNullOrEmpty(config.getPassword())) {
          builder.header("Authorization", basicCredentials(config.getUsername(), config.getPassword()));
        } else if (Utils.isNotNullOrEmpty(config.getOauthToken())) {
          builder.header("Authorization", "Bearer " + config.getOauthToken());
        }
        if (config.getCustomHeaders() != null && !config.getCustomHeaders().isEmpty()) {
          for (Map.Entry<String, String> entry : config.getCustomHeaders().entrySet()) {
            builder.header(entry.getKey(),entry.getValue());
          }
        }
        if (config.getUserAgent() != null && !config.getUserAgent().isEmpty()) {
          builder.setHeader("User-Agent", config.getUserAgent());
        }
      }
    });
// something else
}

[csviri]

LGTM

thank you!