fix: Correctly delete unneeded messages on the server; Remove "Delete Messages from Server" (delete_server_after) config option (#8240)

Fix https://github.com/chatmail/core/issues/8195
Supersedes https://github.com/chatmail/core/pull/8217

The most interesting change is in `delete_expired_imap_messages()`
because there, messages are marked for deletion on single-device
chatmail profiles.

The logic in `delete_expired_imap_messages()` was wrong before, and
pre-messages were not deleted at all. This is fixed by also querying
`pre_rfc724_mid` in addition to `rfc724_mid` from the `msgs` table.
In order not to make the SQL statement too complex, I split it into two.

WRT tests:
- `test_immediate_autodelete()` tests the auto-deletion;
`test_imap_autodelete_fully_downloaded_msg()` tests that even for a
message that is split into pre- and post-message, both messages are
deleted.
- A lot of tests test that if bcc_self is on, messages are not
auto-deleted. E.g. `test_one_account_send_bcc_setting()` and
`test_markseen_message_and_mdn()` relies on the fact that messages stay
on the server when bcc_self is on.
- Unfortunately, it is not possible to test that messages are only
deleted for chatmail servers, because we don't have any tests that use a
non-chatmail server.

deltachat-jsonrpc/src/api.rs

@@ -735,10 +735,19 @@ impl CommandApi {
         Ok(msg_ids)
     }
 
-    /// Estimate the number of messages that will be deleted
-    /// by the set_config()-options `delete_device_after` or `delete_server_after`.
+    /// Estimates the number of messages that will be deleted
+    /// by the `set_config()`-option `delete_device_after`.
+    ///
     /// This is typically used to show the estimated impact to the user
     /// before actually enabling deletion of old messages.
+    ///
+    /// Messages in the "Saved Messages" chat are not counted as they will not be deleted automatically.
+    ///
+    /// Parameters:
+    /// - `from_server`: Deprecated, pass `false` here
+    /// - `seconds`: Count messages older than the given number of seconds.
+    ///
+    /// Returns the number of messages that are older than the given number of seconds.
     async fn estimate_auto_deletion_count(
         &self,
         account_id: u32,