code: function setContext(seneca, context) {
    seneca.fixedargs.tx$ = URLSafeBase64.encode(new Buffer(JSON.stringify(context)));
    seneca.fixedargs.context$ = context;
    debug('context saved', seneca.fixedargs.tx$, context);
  }
docs: Saves the specified context inside the seneca transaction ID.
  
  @param {seneca} seneca The seneca object, which is the context of a running action.
  @param {Object} context A context object