=== Demo 7: SecurityContextHolderFilter vs SecurityContextPersistenceFilter -- load vs. load+save ===
A) SecurityContextPersistenceFilter, context set mid-chain, auto-saved to session after chain returns: true  [true -- this filter saves for you]
B) SecurityContextHolderFilter, context set mid-chain, auto-saved to session after chain returns: false  [false -- requireExplicitSave's default; nothing persists unless you save it yourself]
C) SecurityContextHolderFilter + explicit repository.saveContext(...) inside the chain: true  [true -- the workaround the post recommends actually works]
D) SecurityContextHolderFilter, context already saved in an existing session, next request: authenticated as dave  [it does load -- "only loads, never saves" describes the SAVE side, not the LOAD side]
EDGE) brand-new request, no prior session, nothing set: NO AUTHENTICATION (empty context, not an error)