code: public DocServiceBuilder injectedScript(Iterable<String> scripts) {
          requireNonNull(scripts, "scripts");
          for (String s : scripts) {
              requireNonNull(s, "scripts contains null.");
              injectedScriptSuppliers.add((unused1, unused2) -> s);
          }
          return this;
      }
docs: Adds Javascript scripts to inject into the {@code <head />} of the debug page HTML. This can be used to
  customize the debug page (e.g., to provide a HeaderProvider for enabling authentication based on local
  storage). All scripts are concatenated into the content of a single script tag.
  
  <p>A common use case is to provide authentication of debug requests using a local storage access token,
  e.g., <pre>{@code
  armeria.registerHeaderProvider(function() {
  // Replace with fetching accesstoken using your favorite auth library.
  return Promise.resolve({ authorization: 'accesstoken' });
  });
  }</pre>