core: api to differentiate contacts and conversations (#4111)

src/Simplex/Chat/Migrations/chat_schema.sql

@@ -76,6 +76,7 @@ CREATE TABLE contacts(
   contact_status TEXT NOT NULL DEFAULT 'active',
   custom_data BLOB,
   ui_themes TEXT,
+  chat_deleted INTEGER NOT NULL DEFAULT 0,
   FOREIGN KEY(user_id, local_display_name)
   REFERENCES display_names(user_id, local_display_name)
   ON DELETE CASCADE