[java-sdk] Java Actor runtime

[artursouza]

Creating the Java Actor runtime classes, similar to the one in the Dotnet sdk.

Implementing the API endpoints for the SDK. The business logic should be (preferably) identical to the one in the Dotnet SDK.

Following are some of the few classes in C# SDK;

ActorRuntime: This is the actor runtime in SDK and contains information about registered types. It contains a mapping of ActorType and ActorManager. Actor types are registered with ActorRuntime.

ActorManager: It manages actors instances for an actor type, activates, deactivates them and make method calls to them.

ActorStateManager: Abstracts state management for Actors, provides a cache for Actor states, so that states which have already been worked on are not fetched again from Dapr for an active actor.

Actor: Base class for Actors. (In Java it can be called DaprActor)

DaprStateProvide: ActorStateManager uses it to interact with Dapr for state management.

RouterBuilderExtensions: This is for registering routes with aspnetcore, it registers the required routes (urls) on which Dapr runtime will call into user service code.

[artursouza]

Unit tests to close on this issue: #85 #86