[FIX] base_comment_template: Incorrect m2m column names + script + avoid FK constraint

- The name of the columns were swapped, so better to fix it for avoiding
  mistakes due to this.
- Migration script for detecting the condition and swap column names.
- On v12 > v13 migration, include JOINs for avoiding FK constraint,
  which `ON CONFLICT` clause doesn't protect.

base_comment_template/migrations/13.0.3.0.0/pre-migration.py

@@ -0,0 +1,21 @@
+# Copyright 2021 Tecnativa - Pedro M: Baeza
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
+from openupgradelib import openupgrade  # pylint: disable=W7936
+
+
+@openupgrade.migrate()
+def migrate(env, version):
+    if openupgrade.table_exists(env.cr, "base_comment_template_res_partner_rel"):
+        # Swap column names, as they were incorrect
+        env.cr.execute(
+            "ALTER TABLE base_comment_template_res_partner_rel "
+            "RENAME base_comment_template_id TO temp"
+        )
+        env.cr.execute(
+            "ALTER TABLE base_comment_template_res_partner_rel "
+            "RENAME res_partner_id TO base_comment_template_id"
+        )
+        env.cr.execute(
+            "ALTER TABLE base_comment_template_res_partner_rel "
+            "RENAME temp TO res_partner_id"
+        )