I’m using rails 6.1 and paperclip 5.0

I built a worker to generate a ZIP file based on other stored files in S3 then upload this ZIP file back to S3.

So basically I download the files from S3 add them in this Temp ZIP and then saving the ZIP to S3.

class Download < ApplicationRecord
  # ...
  has_attached_file :file,
                    path: "#{ENV['DEVELOPER']}/Institucion-:institution_id/Usuario-:user_id/:id/:filename",
                    content_type: { content_type: ["application/zip"] }

  # ...
end 

class GenerateZipWorker < ApplicationWorker
  def perform(download_id, options = {})
    @download = Download.find(download_id)
    # ...
    @download.file = generate_full_zip
    # Here the ZIP Temp file gets a PDF content-type
    # @download.file.content_type
    # => "application/pdf"
    @download.file_file_name = "#{@postulation_template.name[0..100].parameterize}.zip"
    @download.save

  end

  private
  def generate_full_zip
    temp_zip_file = Tempfile.new("#{@postulation_template.name[0..100].parameterize}.zip")

    Zip::File.open(temp_zip_file.path, Zip::File::CREATE) do |zip|
      @postulations.each do |postulation|
        generate_postulation_file(zip, postulation)
      end
    end

    temp_zip_file.rewind
    temp_zip_file
  end

  def generate_postulation_file(zip, postulation)
    root_path = postulation.file_name
    zip.get_output_stream(File.join(root_path, postulation.postulation_pdf_file_name)) { |f| f.write postulation.postulation_pdf.s3_object.get.body.string }
  end
end

I tried to set manually the content-type before saving the file

@download.file_content_type = 'application/zip'

But when I download the file from the AWS S3 dashboard it downloads it as a PDF, adding a .pdf at the end of the file name (foo.zip.pdf). If I delete the PDF extention keeping the .zip the downloaded file works just fine.
If I change the content-type from the AWS S3 dashboard from application/pdf to application/zip I can download with no issues.

1️How can I upload the file content-type as application/zip?

2️⃣Is it the Temp file messing the content-type?

3️⃣Is there a better way to build the ZIP temp file?