This is a list of links to K2 documentation which covers K2 Authentication and Authorization topics. In case you have some time to read something for fun 🙂
Authentication
Authentication and Authorization in K2
Claims-based Authentication in K2
Outbound Authorization and OAuth in K2
Troubleshooting Claims-based Authentication Issues
Identity and Data Security in K2 Cloud for SharePoint
SharePoint Hybrid, Multiple Identity Providers & K2
AAD Multi-Factor Authentication Considerations
Enabling AAD Multi-Factor Authentication Requires Changes in K2 4.7
Authentication (in Management)
Azure Active Directory Management (Read/Write to AAD)
Claims and OAuth Configuration for SharePoint 2013
Standard SmartForms Authentication
Multi-Authentication Providers
Authorization
Authorization Framework Overview
Outbound Authorization and OAuth in K2
REST Broker
Resources for Working with the REST Service Broker
REST Swagger File Reference Format
REST Broker and Swagger Descriptor Overview (video)
OData Broker
Using the OData Service Broker (including Serialization and Deserialization)
Workflow and SmartObject APIs
Configuring the Workflow REST API
Configuring the SmartObject OData API
How to Use the K2 Workflow REST Feed with Microsoft Flow to Redirect a K2 Task
How to Use the K2 Workflow REST Feed with Microsoft Flow to Start a Workflow