[db] remove deprecated message field

Author: capcom6

internal/sms-gateway/models/migrations/mysql/20250708232157_remove_message_field.sql

@@ -0,0 +1,20 @@
+-- +goose Up
+-- +goose StatementBegin
+ALTER TABLE `messages` DROP `message`;
+-- +goose StatementEnd
+---
+-- +goose Down
+-- +goose StatementBegin
+ALTER TABLE `messages`
+ADD `message` text NULL;
+-- +goose StatementEnd
+-- +goose StatementBegin
+UPDATE `messages`
+SET `message` = CASE
+        WHEN `is_hashed` = 0 THEN COALESCE(
+            JSON_VALUE(`content`, '$.text'),
+            JSON_VALUE(`content`, '$.data')
+        )
+        ELSE `content`
+    END;
+-- +goose StatementEnd