Add support to set mysql db backups

Description

The [Mattermost Operator](https://github.com/mattermost/mattermost-operator) is a Kubernetes operator that manages the lifecycle of a Mattermost installation.

Currently, the mattermost operator does not support the backup for the DB, the user need to create using the manifests and controller for the presslabs mysql operator.

For this ticket implement the new fields and the code to support the definition of the db mysql backups via mattermost operator

QA Test Steps

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Status

Mana

None

Assignee

Unassigned

Reporter

Carlos Panato

Epic Link

Fix versions

Mattermost Team

Cloud

Sprint

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