serialization.rst: pkcs7_decrypt_der (binary mode)

[gav2xlin]

Hello. Please, mention that the ist of [PKCS7Options] is optional.

options = [pkcs7.PKCS7Options.Text] # to decrypt text data
options = [] # to decrypt binary data (as is)

An example:

:param options: An optional list of
:class:~cryptography.hazmat.primitives.serialization.pkcs7.PKCS7Options. For
this operation only
:attr:~cryptography.hazmat.primitives.serialization.pkcs7.PKCS7Options.Text is supported
or nothing for binary data.

[reaperhulk]

Optional generally means you could passNone. This function requires that you pass a list, but that list can be empty. I'd suggest just stating that an empty list is allowable and handles binary data.

[gav2xlin]

@alex @reaperhulk

Changed and fixed

https://github.com/pyca/cryptography/blob/main/src/rust/src/pkcs7.rs

The functions decrypt_smime() and decrypt_pem() call decrypt_der()