Fix processing of attachments encoded as Latin 1

lib/mail_handler/backends/mail_backend.rb

@@ -402,10 +402,14 @@ def attempt_to_find_original_attachment_attributes(mail, body:, nested: false)
         all_attributes = get_attachment_attributes(mail)
 
         def calculate_hexdigest(body)
-          # ensure bodies have the same line endings
-          Digest::MD5.hexdigest(Mail::Utilities.binary_unsafe_to_lf(
-            body.rstrip
-          ))
+          # ensure bodies have the same line endings and are encoded the same
+          Digest::MD5.hexdigest(
+            Mail::Utilities.binary_unsafe_to_lf(
+              convert_string_to_utf8(
+                body.rstrip
+              ).string
+            )
+          )
         end
 
         hexdigest = calculate_hexdigest(body)

spec/lib/mail_handler/backends/mail_backend_spec.rb

@@ -461,6 +461,7 @@
         add_file filename: 'lf.txt', content: "bar\nbar"
         add_file filename: 'crlf-non-ascii.txt', content: "Aberdâr\r\n"
         add_file filename: 'lf-non-ascii.txt', content: "Aberdâr\n"
+        add_file filename: 'latin1.txt', content: "naïve"
         add_file filename: 'mail.eml', content: mail_attachment
         add_file filename: 'uuencoded.eml', content: mail_with_uuencoded
       end
@@ -492,6 +493,11 @@
       it { is_expected.to include(body: "Aberdâr\n") }
     end
 
+    context 'when binary body encoded as Latin 1 / ISO-8859-1' do
+      let(:body) { "na\xEFve".b }
+      it { is_expected.to include(body: "naïve") }
+    end
+
     context 'when attached email headers are different' do
       let(:body) do
         <<~EML