instance method set_content_type

# File actionpack/lib/action_dispatch/http/response.rb, line 534
    def set_content_type(content_type, charset)
      type = content_type || ""
      if charset
        charset = charset.to_s.downcase
        type = "#{type}; charset=#{charset}"
      else
        charset = nil
      end
      set_header CONTENT_TYPE, type

      # We serialized the parts ourselves, so prime the parsed-header memo
      # instead of letting the reader regexp-parse our own output back apart.
      # Parts the parser could read differently, or that aren't in the encoding
      # of the header it would read them from, go through the parser.
      mime_type = content_type.presence
      unless mime_type&.match?(AMBIGUOUS_CONTENT_TYPE_PART) || charset&.match?(AMBIGUOUS_CONTENT_TYPE_PART) || charset == "" ||
          (mime_type && mime_type.encoding != type.encoding) || (charset && charset.encoding != type.encoding)
        @parsed_content_type_raw = -type
        @parsed_content_type = ContentTypeHeader.new(mime_type, charset)
      end
    end