Use local registry in test fixtures to prevent collision in globally
shared models.
Fix issues discoverd in auth implementation where the global registry
was used instead of the correct local one.
- Removes backward compatibility
for legacy end points `/models` & `/routes`
- Removes `legacyExplorer` flag which
enabled these routes
- Update related tests & tests using the
legacyExplorer flag
Miroslav Bajtoš
gunjpan
David Cheung
Raymond Feng