Package-level declarations

Helpers for HTTP ETag / If-Match handling in support of optimistic concurrency on REST endpoints.

JWT claim helpers for Keycloak tokens, used by both the servlet and reactive KeycloakJwtAuthenticationConverter to keep claim extraction logic in one place.

Helpers for verifying that a client-supplied expected version matches the version currently persisted, enabling optimistic concurrency on the application side before any write hits the database.