chore: update db code to return db errors instead of api errors

[omarelkashef]

No description provided.

[Copilot]

Pull request overview

This PR refactors the database store layer to return store-specific sentinel errors (e.g., not-found / already-exists) rather than HTTP/API-specific status errors, and wires those store errors into LXD’s response.SmartError mapping during service startup.

Changes:

• Replace api.StatusErrorf/StatusErrorCheck usage in internal/pkg/database/store with store.ErrNotFound/store.ErrAlreadyExists wrappers and store.IsNotFound checks.
• Add internal/pkg/database/store/errors.go to centralize store error definitions and helper constructors.
• Initialize response.SmartError mappings at startup in both management-api and cluster-connector.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/pkg/database/store/sessions.go	Switch session store functions from HTTP status errors to store sentinel errors.
internal/pkg/database/store/remote_cluster.go	Switch remote cluster store functions to store sentinel errors and checks.
internal/pkg/database/store/remote_cluster_token.go	Switch remote cluster token store functions to store sentinel errors and checks.
internal/pkg/database/store/remote_cluster_detail.go	Switch remote cluster detail store functions to store sentinel errors and checks.
internal/pkg/database/store/identities.go	Switch identity store functions to store sentinel errors and checks.
internal/pkg/database/store/errors.go	Introduce ErrNotFound/ErrAlreadyExists plus helpers (NotFoundErrorf, etc.).
internal/pkg/api/api.go	Add InitializeSmartErrorMappings() to map store sentinel errors to HTTP statuses for SmartError.
internal/app/management-api/core/auth/session.go	Update auth session logic to use store.IsNotFound instead of LXD shared API status checks.
internal/app/management-api/core/auth/oidc.go	Update OIDC verifier to use store.IsNotFound when handling missing sessions.
cmd/management-api/management-api.go	Call api.InitializeSmartErrorMappings() during service startup.
cmd/cluster-connector/cluster-connector.go	Call api.InitializeSmartErrorMappings() during service startup.

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[edlerd]

I am not sure if this is the right thing to do. It seems an established pattern also in LXD to return http statuses from the database layer. An example is in profiles.mapper.go. To me it seems okay, and not fundamentally wrong, also it seems simpler.

Shall we keep things as they are right now?