## Canvas Connect
## Updates & Improvements
- Adds warnings when LTI launch cannot attach an identity because it is
already owned by another account.

## External Logins
### New Features
- Enforce global uniqueness for External Logins. Cross-user duplicate
external identities are now blocked by design.
- `replace_existing=False` still allows multiple identifiers for the
same user/provider (important for LTI issuer/sub history).