platform: iteration on extracting the platform

Overdue tests pass.

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>
platform: iteration on extracting the platform

Individual payment tests pass, although TestDirectPaymentProcessor fails
when running the whole suite (it looks like a db clenaup issue).

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>
platform: iteration on extracting the platform

Tenant tests pass.

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>