create and test migration skript

[zven]

We need to migrate the users and their devices to the new openSenseMap. For this purpose, we need a migration skript (surprise!) that does exactly that.

The purpose of this ticket is to

• create a migration concept / workflow
• implement that workflow as a skript
• test the skript in a meaningful way (with real data?)

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What do we migrate?

Details see here: https://cloud.opensenselab.org/apps/collectives/openSenseMap-30/Migration-1016812 and here: https://cloud.opensenselab.org/apps/collectives/openSenseMap-30/Release-Plan-992228#h-migrationsskript