code: function setContextPlugin(options) {
    var seneca = this;
    var plugin = 'set-context';
  
    options = seneca.util.deepextend({
      createContext: createContext,
      contextHeader: 'x-request-id'
    }, options);
  
    seneca.act({
      role: 'web',
      plugin: plugin,
      use: processRequest.bind(null, options)
    });
  
    return {name: plugin};
  }
docs: A seneca plugin, which automatically sets the context for all HTTP requests.
  
  @param {{
  // A function which creates a context based on the HTTP request and response.
  // It is used by the `setContextPlugin`.
  // The `defaultContext` is `{requestId: req.headers[options.contextHeader]}`.
  // Default is noop.
  createContext: function (request, response, defaultContext, function(error, context))
  
  // The name of the HTTP request header containing the request context.
  // Default is 'x-request-id'.
  contextHeader: string
  }} options