iceberg: support views (#10069)

* s3tables: tag table entries and exclude views from table listings

* s3tables: add view CRUD operations

* iceberg: support view create, load, exists, drop, and list

* iceberg: support view update

* iceberg: test view error classification and metadata round-trip

* iceberg: pre-check existence and write view metadata only after create

* iceberg: map view namespace-not-found to 404

* iceberg: test view create namespace-404 and duplicate no-clobber

* s3tables: tag view metadata and entry type atomically

CreateView wrote ExtendedKeyMetadata and ExtendedKeyEntryType in two
UpdateEntry calls, so a partial failure could leave a view directory
untagged. Add setExtendedAttributes to set both in one UpdateEntry.

* iceberg: roll back view registration when metadata write fails

The metadata file is written after the catalog registers the view. If
that write fails, drop the just-created view so it doesn't linger
pointing at a missing metadata.json. Reuse the DeleteView path via a
shared dropView helper.

weed/s3api/s3tables/handler.go

@@ -26,6 +26,12 @@ const (
 	ExtendedKeyMetadataVersion = "s3tables.metadataVersion"
 	ExtendedKeyPolicy          = "s3tables.policy"
 	ExtendedKeyTags            = "s3tables.tags"
+	ExtendedKeyEntryType       = "s3tables.entryType"
+
+	// Entry-type marker values for ExtendedKeyEntryType. Absent or "table" means
+	// a table; views are stored like tables but tagged "view".
+	EntryTypeTable = "table"
+	EntryTypeView  = "view"
 
 	// Maximum request body size (10MB)
 	maxRequestBodySize = 10 * 1024 * 1024
@@ -153,6 +159,18 @@ func (h *S3TablesHandler) HandleRequest(w http.ResponseWriter, r *http.Request,
 	case "DeleteTable":
 		err = h.handleDeleteTable(w, r, filerClient)
 
+	// View operations
+	case "CreateView":
+		err = h.handleCreateView(w, r, filerClient)
+	case "GetView":
+		err = h.handleGetView(w, r, filerClient)
+	case "ListViews":
+		err = h.handleListViews(w, r, filerClient)
+	case "UpdateView":
+		err = h.handleUpdateView(w, r, filerClient)
+	case "DeleteView":
+		err = h.handleDeleteView(w, r, filerClient)
+
 	// Table Policy operations
 	case "PutTablePolicy":
 		err = h.handlePutTablePolicy(w, r, filerClient)
@@ -363,6 +381,10 @@ func (h *S3TablesHandler) generateTableARN(ownerAccountID, bucketName, tableID s
 	return fmt.Sprintf("arn:aws:s3tables:%s:%s:bucket/%s/table/%s", h.region, ownerAccountID, bucketName, tableID)
 }
 
+func (h *S3TablesHandler) generateViewARN(ownerAccountID, bucketName, viewID string) string {
+	return fmt.Sprintf("arn:aws:s3tables:%s:%s:bucket/%s/view/%s", h.region, ownerAccountID, bucketName, viewID)
+}
+
 func isAuthError(err error) bool {
 	var authErr *AuthError
 	return errors.As(err, &authErr) || errors.Is(err, ErrAccessDenied)