Two new session-state mutations, both following the rename endpoint's
shape (PUT + {flag: true|false} body + visitorId/sessionId query):
- PUT /api/v1/channels/webchat/sessions/pinned — flips mate_conversation.pinned
- PUT /api/v1/channels/webchat/sessions/archive — flips mate_conversation.archived
Archive complements delete as a "soft-close" — the thread stays on disk
(history preserved, addressable, downloadable) but is hidden from the
default /sessions listing. Pin makes a thread sort first in the visitor's
listing, mirroring the admin-console behavior.
Archive dominates pin: an archived+pinned thread is still hidden by
default. Callers opt back in via includeArchived=true (added in PR 1).
ConversationService gains setArchived(), mirroring the existing
setPinned() pattern.
WebChatArchivePinTest (@SpringBootTest, 6 cases):
- pin flips column + view reflects pinned=1
- archive hides from default listing, includeArchived=true shows it,
un-archive restores
- archived+pinned still hidden (archive dominates)
- malformed body / wrong type → 400
- unknown sessionId → 404
- bad token → 401
Part of epic #355.
