FIX: always test and coerce to image on upload

In the past the filename of the origin was used as the source
for the extension of the file when optimizing on upload.

We now use the actual calculated extension based on upload data.

spec/models/optimized_image_spec.rb

@@ -27,6 +27,32 @@ describe OptimizedImage do
     end
 
     describe '.resize' do
+      it 'should work correctly when extension is bad' do
+
+        original_path = Dir::Tmpname.create(['origin', '.bin']) { nil }
+
+        begin
+          FileUtils.cp "#{Rails.root}/spec/fixtures/images/logo.png", original_path
+
+          # we use "filename" to get the correct extension here, it is more important
+          # then any other param
+
+          OptimizedImage.resize(
+            original_path,
+            original_path,
+            5,
+            5,
+            filename: "test.png"
+          )
+
+          expect(File.read(original_path)).to eq(
+            File.read("#{Rails.root}/spec/fixtures/images/resized.png")
+          )
+        ensure
+          File.delete(original_path) if File.exists?(original_path)
+        end
+      end
+
       it 'should work correctly' do
         tmp_path = "/tmp/resized.png"