deprecate: Add deprecation warning to migrate module

The datajoint.migrate module will be removed in DataJoint 2.2.
Users will see a DeprecationWarning when importing the module,
giving them time to complete their schema migrations.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: dimitri-yatsenko

src/datajoint/migrate.py

@@ -5,6 +5,10 @@
 Codec system, particularly for upgrading blob columns to use
 explicit `<blob>` type declarations.
 
+.. deprecated:: 2.0.0
+    This module is deprecated and will be removed in DataJoint 2.2.
+    Complete your migrations before upgrading to 2.2.
+
 Note on Terminology
 -------------------
 This module uses "external storage" because that was the term in DataJoint 0.14.6.
@@ -16,10 +20,18 @@
 
 import logging
 import re
+import warnings
 from typing import TYPE_CHECKING
 
 from .errors import DataJointError
 
+warnings.warn(
+    "datajoint.migrate is deprecated and will be removed in DataJoint 2.2. "
+    "Complete your schema migrations before upgrading to 2.2.",
+    DeprecationWarning,
+    stacklevel=2,
+)
+
 if TYPE_CHECKING:
     from .schemas import Schema