The Apex code illustrates how to generate XML containing Account information and its related Contacts. It includes the Account details in the root tag and adds the Contacts within a
Tag: Integration
This article walk you through using the Slack API within Salesforce Apex. This contains an example of unarchiving the Slack channel using API: https://api.slack.com/methods/conversations.unarchive
This article has two apex invocable actions that can be invoked from the flow and other apex classes.
Integration between Salesforce and Stripe. Sample code to create an charge object in stripe using apex code. The apex code can be invoked from the flow.