Add ResilientLdapGroupRoleMappingService — a singleton decorator that wraps the
hot-path GetByGroupsAsync call in a Polly pipeline (timeout 2s → retry 3× jittered
→ fallback to in-memory sealed snapshot) so a transient Config DB outage at
Admin sign-in falls back to the last-known-good mapping set rather than denying
every login. The static LdapOptions.GroupToRole bootstrap dictionary in
AdminRoleGrantResolver remains the lock-out-proof floor regardless of DB state.
DI wiring uses keyed services: LdapGroupRoleMappingService (EF, scoped) is
registered under key "LdapGroupRoleMappingService.Inner"; the resilient singleton
decorator is the primary ILdapGroupRoleMappingService binding. The singleton
avoids the captive-dependency anti-pattern by using IServiceScopeFactory to open
a short-lived scope for each DB call.
Write methods (CreateAsync, DeleteAsync, ListAllAsync) pass through unchanged —
resilience is read-path only per Phase 6.1 design decision.
15 new unit tests cover: DB success/failure/retry paths, snapshot sealing and
per-group-set isolation, order-independent cache key normalisation, cancellation
propagation, and pass-through method routing.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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