feat: T-927 Add a mutation to Update an existing product

[vincent-pochet]

Add a new mutation to update an existing Product and reasign BillableMetrics

[height]

This pull request has been linked to 2 tasks:

• T-928 [API] Add a query to retrieve products (unlink task)
• T-927 [API] Add mutation to update a Product (unlink task)

💡Tip: Add "Close T-928" to the pull request title or description, to a commit message, or in a comment to mark this task as "Done" when the pull request is merged.

[jdenquin]

LGTM 🚀