core: signed history in channels, auto-sign based on preference (#7257)

src/Simplex/Chat/Store/SQLite/Migrations/chat_schema.sql

@@ -508,7 +508,11 @@ CREATE TABLE chat_items(
   show_group_as_sender INTEGER NOT NULL DEFAULT 0,
   has_link INTEGER NOT NULL DEFAULT 0,
   msg_signed TEXT,
-  item_viewed INTEGER NOT NULL DEFAULT 0
+  item_viewed INTEGER NOT NULL DEFAULT 0,
+  item_msg_body BLOB,
+  item_chat_binding TEXT,
+  item_signatures BLOB,
+  item_signed_by_group_member_id INTEGER REFERENCES group_members ON DELETE SET NULL
 ) STRICT;
 CREATE TABLE sqlite_sequence(name,seq);
 CREATE TABLE chat_item_messages(
@@ -1368,6 +1372,9 @@ CREATE INDEX idx_files_group_id_shared_msg_id ON files(
   shared_msg_id
 );
 CREATE INDEX idx_files_roster_transfer_id ON files(roster_transfer_id);
+CREATE INDEX idx_chat_items_item_signed_by_group_member_id ON chat_items(
+  item_signed_by_group_member_id
+);
 CREATE TRIGGER on_group_members_insert_update_summary
 AFTER INSERT ON group_members
 FOR EACH ROW