Simplify next state handling only return state name

The State classes don't need to return the next state object, just the
name.  The Workflow class can lookup the state object by the name since
it owns the hash of state objects.

lib/floe/workflow.rb

@@ -59,11 +59,9 @@ def step
 
       context.states << context.state
 
-      @status = current_state.status
-      @output = output if end?
-
-      next_state_name = next_state&.name
-      @current_state = next_state_name && @states_by_name[next_state_name]
+      @status        = current_state.status
+      @current_state = next_state && @states_by_name[next_state]
+      @output        = output if end?
 
       self
     end

lib/floe/workflow/state.rb

@@ -48,12 +48,12 @@ def run!(input)
         input = input_path.value(context, input)
 
         output, next_state = block_given? ? yield(input) : input
-        next_state ||= workflow.states_by_name[payload["Next"]] unless end?
+        next_state ||= payload["Next"] unless end?
 
         output ||= input
         output   = output_path&.value(context, output)
 
-        logger.info("Running state: [#{name}] with input [#{input}]...Complete - next state: [#{next_state&.name}] output: [#{output}]")
+        logger.info("Running state: [#{name}] with input [#{input}]...Complete - next state: [#{next_state}] output: [#{output}]")
 
         [next_state, output]
       end

lib/floe/workflow/states/choice.rb

@@ -18,10 +18,8 @@ def initialize(workflow, name, payload)
 
         def run!(*)
           super do |input|
-            next_state_name = choices.detect { |choice| choice.true?(context, input) }&.next || default
-            next_state      = workflow.states_by_name[next_state_name]
-
-            output = input
+            output     = input
+            next_state = choices.detect { |choice| choice.true?(context, input) }&.next || default
 
             [output, next_state]
           end

spec/workflow/states/choice_spec.rb

@@ -17,7 +17,7 @@
 
       it "returns the next state" do
         next_state, = subject
-        expect(next_state).to eq(workflow.states_by_name["FirstMatchState"])
+        expect(next_state).to eq("FirstMatchState")
       end
     end
 
@@ -26,7 +26,7 @@
 
       it "returns the default state" do
         next_state, = subject
-        expect(next_state).to eq(workflow.states_by_name["FailState"])
+        expect(next_state).to eq("FailState")
       end
     end
   end