Add a shortcut to enable auto_flush on a Flow with Flow#auto_flush!

lib/rackstash/flow.rb

@@ -137,6 +137,14 @@ module Rackstash
       @auto_flush
     end
 
+    # Enable the {#auto_flush} feature for the current flow.
+    #
+    # @return [true]
+    # @see #auto_flush
+    def auto_flush!
+      self.auto_flush = true
+    end
+
     # @param bool [Bool] `true` to cause buffering Buffers to write their added
     #   messages and fields to the flow as soon as they are logged, `false` to
     #   write the whole event only on an explicit call to {Buffer#flush}.

spec/rackstash/flow_spec.rb

@@ -113,6 +113,13 @@ RSpec.describe Rackstash::Flow do
     end
   end
 
+  describe '#auto_flush!' do
+    it 'enables the auto_flush property' do
+      flow.auto_flush!
+      expect(flow.auto_flush?).to eql true
+    end
+  end
+
   describe '#close!' do
     it 'calls adapter#close' do
       expect(adapter).to receive(:close).and_return(true)