Improve content type detection for .dotx and .ai

To correctly detect content type of file in some cases file
extension should be used in addition to magic detection.
Such cases include custom extensions with .zip contents,
.dotx / .docx files which have same magic signature.

lib/carrierwave/sanitized_file.rb

@@ -321,7 +321,16 @@ def guessed_safe_content_type
 
     def identified_content_type
       with_io do |io|
-        Marcel::Magic.by_magic(io).try(:type)
+        mimetype_by_magic = Marcel::Magic.by_magic(io)
+        mimetype_by_path = Marcel::Magic.by_path(path)
+
+        return nil if mimetype_by_magic.nil?
+
+        if mimetype_by_path&.child_of?(mimetype_by_magic.type)
+          mimetype_by_path.type
+        else
+          mimetype_by_magic.type
+        end
       end
     rescue Errno::ENOENT
       nil