Use Salesforce Apex to implement a Flow invocable action with typed input and output variables callable from declarative automation

In-depth guide

Steps

1. Create a global Apex class with a static method annotated @InvocableMethod and provide a label and description for the Flow UI
2. Define an inner class for inputs annotated with @InvocableVariable for each field with required=true where appropriate
3. Define a separate inner class for outputs also using @InvocableVariable so Flow can map results to variables after the action
4. The invocable method must accept a List of the input class and return a List of the output class to support bulk Flow contexts
5. Write test coverage for the invocable method by calling it directly with a constructed list of input objects
6. After deployment the action appears in the Flow builder Action element picker under your label name