apps/contrib: Add option to disable Matomo cookies

[rmader]

In order to avoid having to show a cookie banner.

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This is actually for a+, but as meinberlin-dev is already set up on matomo, lets test the code here first.

[fuzzylogic2000]

Looks good! And do you want to put cookie_disabled into the pillar settings then?

[fuzzylogic2000]

Well, could you actually add a test? If this is not [easily] testable for something else. Maybe we manage > 84%.

[rmader]

TBH, it doesn't make much sense to me just for the sake of pushing the number up :/
If I write tests, I would rather write them for something we can actually break by accident.

[fuzzylogic2000]

Yes, awesome, then do that!