MC-102: Add writer to send attributes to Magento

| Q                    | A
| -------------------- | ---
| Bug fix?             | n
| New feature?         | y
| Specs pass?*         | y
| Checkstyle issues?** | n
| PMD issues?***       | n
| Fixed tickets        | MC-102
| Doc PR               | n
My fault but discussing with @BitOne, it is cleaner to set this method as non-static. Sorry about that.