NetworkManager rejects AddConnection for 802-1x without a non-empty
identity, so the new API v7 agent-prompt flow never reaches the
SecretAgent for fresh enterprise connections. Fall back to the existing
modal-upfront path (already wired to ask for username + password via
requiresEnterprise) when modelData.enterprise, mirroring the legacy
DMSService.apiVersion < 7 branch.
Fixes#2358
Co-authored-by: Claude Opus 4.7 (1M context) <[email protected]>