docs: add copyright and module docstrings to test_changepoint_process file

Author: iraedeus

tests/test_generator/test_changepoint_process.py

@@ -1,3 +1,10 @@
+"""Tests for changepoint_process module"""
+
+__author__ = "Danil Totmyanin"
+__copyright__ = "Copyright (c) 2025 PySATL project"
+__license__ = "SPDX-License-Identifier: MIT"
+
+
 import hypothesis.strategies as st
 import numpy as np
 import numpy.typing as npt