Real-world like linked usage data for testing purposes

[bjrne]

Is your feature request related to a problem? Please describe.
Bugs occur when testing data does not reflect the use case scenario. Currently, we only have a fake user generation, but no fake data generation, for example sent emails, more diverse hospital texts on the map...

Describe the solution you'd like
More connected user and usage data, either created by a command like the fake users, or by database dump as a fixture.

Additional context
When exporting the current database as a fixture, there are lots of additional options. They should be looked into in order to guarantee a smooth usage experience for all devs, regardless of existing data in their respective testing databases.

[bjrne]

Followup for #504 & #505.