Name each database target's archive for its webhook and target (closes #376)

Each database target now has its own archive file,
archive-WEBHOOKNAME-TARGETNAME-TARGETID.db, instead of one
archive-WEBHOOKID.db per webhook. delivery.ArchiveFileName builds the
name.

A change of webhook or target name renames its archive files under the
archive writer's lock, before the new name is saved, and back again if
the save fails. Webhook edits, target edits and target creation run one
at a time, so no two of them interleave. A rename never replaces a
file, and one that fails part way moves back what it moved. Deleting a
target evicts only that target's writer. Archive files are never
deleted, and nothing looks for files under the old name.

Model: opus-5-5

internal/delivery/export_test.go

@@ -474,7 +474,7 @@ func NewTestCircuitBreaker(
 type ExportArchivedEvent = archivedEvent
 
 // ExportArchiveWriter wraps an archiveWriter so black-box tests
-// can exercise the per-webhook archive file mechanics.
+// can exercise the archive file mechanics.
 type ExportArchiveWriter struct {
 	w *archiveWriter
 }
@@ -549,6 +549,12 @@ func (e *ExportArchiveWriter) Evict() {
 	e.w.evict()
 }
 
+// Rename gives the archive file a new name in the same directory,
+// as a rename of the webhook or target does.
+func (e *ExportArchiveWriter) Rename(name string) error {
+	return e.w.rename(name)
+}
+
 // HandleOpen reports whether the writer currently holds an open
 // archive handle.
 func (e *ExportArchiveWriter) HandleOpen() bool {
@@ -568,16 +574,16 @@ func (e *ExportArchiveWriter) Same(
 }
 
 // ExportArchiveWriterFor returns the archive writer the registry
-// currently caches for a webhook, or nil when none is cached. It
-// never creates one, so a test can hold a reference to the very
-// writer an eviction is about to detach.
+// currently caches for a database target, or nil when none is
+// cached. It never creates one, so a test can hold a reference to
+// the very writer an eviction is about to detach.
 func (e *Engine) ExportArchiveWriterFor(
-	webhookID string,
+	targetID string,
 ) *ExportArchiveWriter {
 	e.dbTarget.mu.Lock()
 	defer e.dbTarget.mu.Unlock()
 
-	w, ok := e.dbTarget.writers[webhookID]
+	w, ok := e.dbTarget.writers[targetID]
 	if !ok {
 		return nil
 	}
@@ -586,26 +592,26 @@ func (e *Engine) ExportArchiveWriterFor(
 }
 
 // ExportHasArchiveWriter reports whether the database target
-// currently caches an archive writer for a webhook.
+// type currently caches an archive writer for a target.
 func (e *Engine) ExportHasArchiveWriter(
-	webhookID string,
+	targetID string,
 ) bool {
 	e.dbTarget.mu.Lock()
 	defer e.dbTarget.mu.Unlock()
 
-	_, ok := e.dbTarget.writers[webhookID]
+	_, ok := e.dbTarget.writers[targetID]
 
 	return ok
 }
 
 // ExportArchiveHandleOpen reports whether the cached archive
-// writer for a webhook holds an open database handle. It
+// writer for a target holds an open database handle. It
 // returns false when no writer is cached.
 func (e *Engine) ExportArchiveHandleOpen(
-	webhookID string,
+	targetID string,
 ) bool {
 	e.dbTarget.mu.Lock()
-	w, ok := e.dbTarget.writers[webhookID]
+	w, ok := e.dbTarget.writers[targetID]
 	e.dbTarget.mu.Unlock()
 
 	if !ok {
@@ -619,12 +625,12 @@ func (e *Engine) ExportArchiveHandleOpen(
 }
 
 // ExportEnsureArchiveWriter creates (if needed) and returns the
-// archive file path of the cached writer for a webhook, so a
+// archive file path of the cached writer for a target, so a
 // test can prime the registry the way a delivery would.
 func (e *Engine) ExportEnsureArchiveWriter(
-	webhookID string,
+	targetID string,
 ) (string, error) {
-	w, err := e.dbTarget.writerFor(webhookID)
+	w, err := e.dbTarget.writerFor(targetID)
 	if err != nil {
 		return "", err
 	}
@@ -632,14 +638,14 @@ func (e *Engine) ExportEnsureArchiveWriter(
 	return w.path, nil
 }
 
-// ExportSweepWriterFor takes a webhook's registry writer exactly
+// ExportSweepWriterFor takes a target's registry writer exactly
 // as the idle sweep does, reporting whether the sweep had to
 // create the entry. It lets a test drive the registry through the
 // sweep's own entry point instead of choreographing goroutines.
 func (e *Engine) ExportSweepWriterFor(
-	webhookID string,
+	targetID string,
 ) (*ExportArchiveWriter, bool, error) {
-	w, created, err := e.dbTarget.sweepWriterFor(webhookID)
+	w, created, err := e.dbTarget.sweepWriterFor(targetID)
 	if err != nil {
 		return nil, false, err
 	}
@@ -650,9 +656,9 @@ func (e *Engine) ExportSweepWriterFor(
 // ExportReleaseSweepWriter releases a sweep-created registry entry
 // exactly as a finished sweep does.
 func (e *Engine) ExportReleaseSweepWriter(
-	webhookID string, w *ExportArchiveWriter,
+	targetID string, w *ExportArchiveWriter,
 ) {
-	e.dbTarget.releaseSweepWriter(webhookID, w.w)
+	e.dbTarget.releaseSweepWriter(targetID, w.w)
 }
 
 // NewTestArchiveSweeper builds an ArchiveSweeper backed by the