Add headers to output

The original implmentation was missing headers to denote mime version &
content transfer encoding, this caused issues with EC2.

Signed-off-by: Simon Thulbourn <simon+github@thulbourn.com>

builtin/providers/template/resource_cloudinit_config.go

@@ -170,6 +170,7 @@ func renderPartsToWriter(parts cloudInitParts, writer io.Writer) error {
 	}
 
 	writer.Write([]byte(fmt.Sprintf("Content-Type: multipart/mixed; boundary=\"%s\"\n", mimeWriter.Boundary())))
+	writer.Write([]byte("MIME-Version: 1.0\r\n"))
 
 	for _, part := range parts {
 		header := textproto.MIMEHeader{}
@@ -179,6 +180,9 @@ func renderPartsToWriter(parts cloudInitParts, writer io.Writer) error {
 			header.Set("Content-Type", part.ContentType)
 		}
 
+		header.Set("MIME-Version", "1.0")
+		header.Set("Content-Transfer-Encoding", "7bit")
+
 		if part.Filename != "" {
 			header.Set("Content-Disposition", fmt.Sprintf(`attachment; filename="%s"`, part.Filename))
 		}