Fix file iterator bytesize fetching

Neither Rack::Files nor Rack::File have ever responded to #map, but the respond to #each, so we should use that instead.

Also, on Rack >= 2.1, Rack::Files::Iterator#bytesize was introduced, avoiding the need to calculate it ourselves.

lib/shrine/plugins/derivation_endpoint.rb

@@ -365,7 +365,14 @@ def call(env)
         handle_request(request)
       end
 
-      headers["Content-Length"] ||= body.map(&:bytesize).inject(0, :+).to_s
+      if Rack.release >= "2.1"
+        headers["Content-Length"] ||= body.byesize.to_s
+      else
+        sum = 0
+        body.each { |chunk| sum += chunk.bytesize }
+
+        headers["Content-Length"] = sum.to_s
+      end
 
       [status, headers, body]
     end
@@ -444,7 +451,11 @@ def expires_in(request)
 
     # Halts the request with the error message.
     def error!(status, message)
-      throw :halt, [status, { "Content-Type" => "text/plain" }, [message]]
+      if Rak.release > "2"
+        throw :halt, [status, {"content-type" => "text/plain"}, [message]]
+      else
+        throw :halt, [status, {"Content-Type" => "text/plain"}, [message]]
+      end
     end
 
     def secret_key

lib/shrine/plugins/download_endpoint.rb

@@ -113,7 +113,14 @@ def call(env)
         handle_request(request)
       end
 
-      headers["Content-Length"] ||= body.map(&:bytesize).inject(0, :+).to_s
+      if Rack.release >= "2.1"
+        headers["Content-Length"] ||= body.byesize.to_s
+      else
+        sum = 0
+        body.each { |chunk| sum += chunk.bytesize }
+
+        headers["Content-Length"] = sum.to_s
+      end
 
       [status, headers, body]
     end

lib/shrine/plugins/presign_endpoint.rb

@@ -91,7 +91,14 @@ def call(env)
         end
       end
 
-      headers["Content-Length"] ||= body.map(&:bytesize).inject(0, :+).to_s
+      if Rack.release >= "2.1"
+        headers["Content-Length"] ||= body.byesize.to_s
+      else
+        sum = 0
+        body.each { |chunk| sum += chunk.bytesize }
+
+        headers["Content-Length"] = sum.to_s
+      end
 
       [status, headers, body]
     end

lib/shrine/plugins/upload_endpoint.rb

@@ -91,7 +91,14 @@ def call(env)
         handle_request(request)
       end
 
-      headers["Content-Length"] ||= body.map(&:bytesize).inject(0, :+).to_s
+      if Rack.release >= "2.1"
+        headers["Content-Length"] ||= body.byesize.to_s
+      else
+        sum = 0
+        body.each { |chunk| sum += chunk.bytesize }
+
+        headers["Content-Length"] = sum.to_s
+      end
 
       [status, headers, body]
     end