[IMP] base_comment_template: Refactor code and convert to Many2Many

base_comment_template/migrations/13.0.2.0.0/pre-migration.py

@@ -0,0 +1,12 @@
+# Copyright 2021 Tecnativa - Víctor Martínez
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
+from openupgradelib import openupgrade  # pylint: disable=W7936
+
+field_renames = [
+    ("base.comment.template", "base_comment_template", "priority", "sequence"),
+]
+
+
+@openupgrade.migrate()
+def migrate(env, version):
+    openupgrade.rename_fields(env, field_renames)