Put Matomo into maintenance mode before upgrading

[pmig]

In https://github.com/glasskube/operator/pull/489 we introduced automatic database upgrade during initialization.

We do not put Matomo into maintenance mode yet. This will make the upgrade more secure as user are not allowed to perform actions against the database.

See https://matomo.org/faq/how-to/faq_111/ for more information.

[Anefu]

Hey @pmig happy to work on this.

[pmig]

@Anefu sure go ahead

If you have any questions feel free to reach out on Discord in our dev channel: https://discord.gg/CetrCcjqpx