feat: key-contacts

This change introduces a new type of contacts
identified by their public key fingerprint
rather than an e-mail address.

Encrypted chats now stay encrypted
and unencrypted chats stay unencrypted.
For example, 1:1 chats with key-contacts
are encrypted and 1:1 chats with address-contacts
are unencrypted.
Groups that have a group ID are encrypted
and can only contain key-contacts
while groups that don't have a group ID ("adhoc groups")
are unencrypted and can only contain address-contacts.

JSON-RPC API `reset_contact_encryption` is removed.
Python API `Contact.reset_encryption` is removed.
"Group tracking plugin" in legacy Python API was removed because it
relied on parsing email addresses from system messages with regexps.

Co-authored-by: Hocuri <hocuri@gmx.de>
Co-authored-by: iequidoo <dgreshilov@gmail.com>
Co-authored-by: B. Petersen <r10s@b44t.com>

src/constants.rs

@@ -210,11 +210,6 @@ pub(crate) const DC_BACKGROUND_FETCH_QUOTA_CHECK_RATELIMIT: u64 = 12 * 60 * 60;
 /// in the group membership consistency algo to reject outdated membership changes.
 pub(crate) const TIMESTAMP_SENT_TOLERANCE: i64 = 60;
 
-/// How long a 1:1 chat can't be used for sending while the SecureJoin is in progress. This should
-/// be 10-20 seconds so that we are reasonably sure that the app remains active and receiving also
-/// on mobile devices. See also [`crate::chat::CantSendReason::SecurejoinWait`].
-pub(crate) const SECUREJOIN_WAIT_TIMEOUT: u64 = 15;
-
 // To make text edits clearer for Non-Delta-MUA or old Delta Chats, edited text will be prefixed by EDITED_PREFIX.
 // Newer Delta Chats will remove the prefix as needed.
 pub(crate) const EDITED_PREFIX: &str = "✏️";