Ability to add custom Fulfillment text

src/dialogflow-fulfillment.js

@@ -374,6 +374,24 @@ class WebhookClient {
   getContext(contextName) {
     return this.contexts.filter( (context) => context.name === contextName )[0] || null;
   }
+
+  /**
+   * Set the fulfillmentText
+   *
+   * @example
+   * const { WebhookClient } = require('dialogflow-webhook');
+   * const agent = new WebhookClient({request: request, response: response});
+   * let context = agent.setFulfillmentText('sample fulfillment text');
+   *
+   * @param {string} text a string representing the fulfillmentText
+   */
+  setFulfillmentText(text) {
+    if (typeof text !== 'string' || !text) {
+      throw new Error('Fulfillment text must be a string');
+    }
+
+    this.client.setFulfillmentText_(text);
+  }
 
   /**
    * Set the followup event

src/v2-agent.js

@@ -203,6 +203,7 @@ class V2Agent {
   sendJson_(responseJson) {
     responseJson.outputContexts = this.agent.outgoingContexts_;
     this.agent.followupEvent_ ? responseJson.followupEventInput = this.agent.followupEvent_ : undefined;
+    this.agent.fulfillmentText_ ? responseJson.fulfillmentText = this.agent.fulfillmentText_ : undefined;
 
     debug('Response to Dialogflow: ' + JSON.stringify(responseJson));
     this.agent.response_.json(responseJson);
@@ -259,6 +260,16 @@ class V2Agent {
     v1Context.parameters = v2Context.parameters;
     return v1Context;
   }
+
+  /**
+   * Add a v2 fulfillmentText
+   *
+   * @param {string} text a string representing the fulfillmentText
+   * @private
+   */
+  setFulfillmentText_(text) {
+    this.agent.fulfillmentText_ = text;
+  }
 
   /**
    * Add an v2 followup event