[mbed-tls] PKCS7 Generation Contribution

Hello,

For one of my projects, I had to create a PKCS7 generation/builder. I noticed mbedtls currently has no support for PKCS7. After much trial and error, I was able to use mbedtls functions to create a PKCS7 structure for Signed Data. I was wondering if this something that might be useful in later versions of mbedtls? The code currently has a long way to go until it meets mbedtls coding standards, but I figured I would ask if it is even possible and worth the efforts before getting into it. I am also a rookie when it comes to open source contributions, so I was hoping for some guidance regarding merging upstream.

Thanks for your time,

Nick Child