[REM] website_mail: remove sha_in based message_post

The _message_post_helper() method historically allowed
passing a `sha_in` signature to let an unauthenticated
user post a message on a record.

This option is unused and an alternative is preferred:
passing a `token` value that matches the value of a
given field of the record.

In light of the increasingly grim future of SHA-1
as a cryptographic hash function, we consider it
better to entirely remove this specific option.

It has been unused for a while, and a simple
alternative exists.

As a temporary measure, the feature was also
deactivated in 10.0 at 2cffcfd860a8c035074ca123e01d8bf5f47ecc4e

0 files changed, 0 insertions, 0 deletions