feat: Save the secret to encrypt and decrypt messages. Next: Send it in a 'member added' message.

src/decrypt.rs

@@ -14,7 +14,7 @@ use crate::pgp;
 pub fn try_decrypt<'a>(
     mail: &'a ParsedMail<'a>,
     private_keyring: &'a [SignedSecretKey],
-    symmetric_secrets: &[&str],
+    symmetric_secrets: &[String],
 ) -> Result<Option<::pgp::composed::Message<'static>>> {
     let Some(encrypted_data_part) = get_encrypted_mime(mail) else {
         return Ok(None);