Add SQLiteChatMessageHistory (#3534)

It's based on already existing `PostgresChatMessageHistory`

Use case somewhere in between multiple files and Postgres storage.

tests/unit_tests/memory/chat_message_histories/test_sql.py

@@ -0,0 +1,85 @@
+from pathlib import Path
+from typing import Tuple
+
+import pytest
+
+from langchain.memory.chat_message_histories import SQLChatMessageHistory
+from langchain.schema import AIMessage, HumanMessage
+
+
+# @pytest.fixture(params=[("SQLite"), ("postgresql")])
+@pytest.fixture(params=[("SQLite")])
+def sql_histories(request, tmp_path: Path):  # type: ignore
+    if request.param == "SQLite":
+        file_path = tmp_path / "db.sqlite3"
+        con_str = f"sqlite:///{file_path}"
+    elif request.param == "postgresql":
+        con_str = "postgresql://postgres:postgres@localhost/postgres"
+
+    message_history = SQLChatMessageHistory(
+        session_id="123", connection_string=con_str, table_name="test_table"
+    )
+    # Create history for other session
+    other_history = SQLChatMessageHistory(
+        session_id="456", connection_string=con_str, table_name="test_table"
+    )
+
+    yield (message_history, other_history)
+    message_history.clear()
+    other_history.clear()
+
+
+def test_add_messages(
+    sql_histories: Tuple[SQLChatMessageHistory, SQLChatMessageHistory]
+) -> None:
+    sql_history, other_history = sql_histories
+    sql_history.add_user_message("Hello!")
+    sql_history.add_ai_message("Hi there!")
+
+    messages = sql_history.messages
+    assert len(messages) == 2
+    assert isinstance(messages[0], HumanMessage)
+    assert isinstance(messages[1], AIMessage)
+    assert messages[0].content == "Hello!"
+    assert messages[1].content == "Hi there!"
+
+
+def test_multiple_sessions(
+    sql_histories: Tuple[SQLChatMessageHistory, SQLChatMessageHistory]
+) -> None:
+    sql_history, other_history = sql_histories
+    sql_history.add_user_message("Hello!")
+    sql_history.add_ai_message("Hi there!")
+    sql_history.add_user_message("Whats cracking?")
+
+    # Ensure the messages are added correctly in the first session
+    assert len(sql_history.messages) == 3, "waat"
+    assert sql_history.messages[0].content == "Hello!"
+    assert sql_history.messages[1].content == "Hi there!"
+    assert sql_history.messages[2].content == "Whats cracking?"
+
+    # second session
+    other_history.add_user_message("Hellox")
+    assert len(other_history.messages) == 1
+    assert len(sql_history.messages) == 3
+    assert other_history.messages[0].content == "Hellox"
+    assert sql_history.messages[0].content == "Hello!"
+    assert sql_history.messages[1].content == "Hi there!"
+    assert sql_history.messages[2].content == "Whats cracking?"
+
+
+def test_clear_messages(
+    sql_histories: Tuple[SQLChatMessageHistory, SQLChatMessageHistory]
+) -> None:
+    sql_history, other_history = sql_histories
+    sql_history.add_user_message("Hello!")
+    sql_history.add_ai_message("Hi there!")
+    assert len(sql_history.messages) == 2
+    # Now create another history with different session id
+    other_history.add_user_message("Hellox")
+    assert len(other_history.messages) == 1
+    assert len(sql_history.messages) == 2
+    # Now clear the first history
+    sql_history.clear()
+    assert len(sql_history.messages) == 0
+    assert len(other_history.messages) == 1