Minimize the boundary between src/core and src/{feature,app}
The API boundary between src/core and higher level layers is more or less nonexistent. That's not surprising, since we created this distinction by moving files and functions around.
We can actually do much better here. Possibile strategies include:
- Removing up-calls from src/core to src/{feature,app}
- Designing an API for the code, and adjusting external modules to use that.
- Moving more pieces outside of sec/core as appropriate