create chat index table

src/sqlite/chat_index.sql

@@ -0,0 +1,8 @@
+-- chat index table
+CREATE TABLE IF NOT EXISTS chat_index (
+    id TEXT NOT NULL,
+    is_group_chat BOOLEAN DEFAULT 0 NOT NULL CHECK (is_group_chat IN (0, 1)),
+    title TEXT NOT NULL,
+    description TEXT,
+    users TEXT NOT NULL
+);