api: make exported concrete classes final

To prevent them from being extended.

Signed-off-by: Ferry Huberts <ferry.huberts@pelagic.nl>
api: add provider/consumer type annotation

Signed-off-by: Ferry Huberts <ferry.huberts@pelagic.nl>
Enable baselining

Signed-off-by: Ferry Huberts <ferry.huberts@pelagic.nl>