Key files:
SlackPublisher.cls Apex class that publishes simple notifications to a Slack webhook. Can be called from Salesforce Process Builder.
SlackPublisherTest.cls Apex test class for SlackPublisher.
SalesforcePublisher.cls Apex class that publishes records from one Salesforce org to another. Can be called from Salesforce Process Builder.
SalesforcePublisherTest.cls Apex test class for SalesforcePublisher.
SalesforcePublisherDocs/ Step-by-step instructions for configuring the Connected App, Auth Provider, and Named Credential necessary to make the sample SalesforcePublisher code work.