[DEVEX-227] Updated ProjectState to keep dictionary of states instead of the single state

That gives possibility to cache multiple single stream projection states instead of rolling always a single one

Author: oskardudycz

src/Kurrent.Client/Streams/GettingState/StateBuilder.cs

@@ -180,19 +180,22 @@ public static async IAsyncEnumerable<StateAtPointInTime<TState>> ProjectState<TS
 		Func<TState, ResolvedEvent, TState> evolve,
 		[EnumeratorCancellation] CancellationToken ct
 	) where TState : notnull {
-		var state = initialState;
-
 		if (messages is KurrentClient.ReadStreamResult readStreamResult) {
 			if (await readStreamResult.ReadState.ConfigureAwait(false) == ReadState.StreamNotFound) {
-				yield return new StateAtPointInTime<TState>(state);
+				yield return new StateAtPointInTime<TState>(initialState);
 
 				yield break;
 			}
 		}
 
+		var states = new Dictionary<string, TState>();
+
 		await foreach (var resolvedEvent in messages.WithCancellation(ct)) {
+			var state = states.GetValueOrDefault(resolvedEvent.OriginalStreamId, initialState);
 			state = evolve(state, resolvedEvent);
 
+			states[resolvedEvent.OriginalStreamId] = state;
+
 			yield return new StateAtPointInTime<TState>(
 				state,
 				resolvedEvent.Event.EventNumber,
@@ -210,14 +213,13 @@ public static async Task<StateAtPointInTime<TState>> GetStateAsync<TState>(
 	) where TState : notnull {
 		StateAtPointInTime<TState>? stateAtPointInTime = null;
 
-		options ??= new GetStreamStateOptions<TState> ();
-		
-		if (options.GetSnapshot != null) {
+		options ??= new GetStreamStateOptions<TState>();
+
+		if (options.GetSnapshot != null)
 			stateAtPointInTime = await options.GetSnapshot(
 				GetSnapshotOptions.ForStream(streamName),
 				ct
 			);
-		}
 
 		options.StreamPosition = stateAtPointInTime?.LastStreamPosition ?? StreamPosition.Start;