by default the REST service is mounted at /, so we should not point in the API
doc to /graph as root mount point, because it will puzzle testers
I'm not sure to understand why we cannot use like the others URL (https://docs.softwareheritage.org/devel/http-routingtable.html) a sub-endpoint /graph.
No, you're right, I didn't think of the global namespace of unified documentation.
Abandoning this diff.