Instead to implement own logic how the database scheme should be updated
or migrated to a newer or older version flucky use now instead the
go-migrate package.
Add additional functions to the repository to add or update devices,
sensors or measured values. Furthermore the test has been adapt to the
new functions.
Changes:
- Renamed storage endpoint into dsn (data source name).
- Add additional dsn fallback property. This dsn will be used in futes
to store informations, if the main dsn backend does not work
correctly. For example, if no connection can be established over the
network to a database.
