public interface Action
  
  
  Represents an action taken by the user within the app.
Actions are constucted via Action.Builder
      and logged via 
      FirebaseUserActions.start(Action) and 
      FirebaseUserActions.end(Action). Convenience methods to construct common types of
      actions are available via Actions.
Nested Class Summary
| class | Action.Builder | The builder for Action. | |
| interface | Action.Metadata | Represents the metadata for an Action. | |