feat: add idempotent batch task submission and recovery examples

internal/transport/httpserver/tasks.go

@@ -27,6 +27,17 @@ import (
 type endpoint func(*http.Request, auth.Token) (any, int, error)
 
 func registerTasks(mux *http.ServeMux, s *service.Service) {
+	mux.HandleFunc("POST /v1/tasks:batch", wrap(func(r *http.Request, t auth.Token) (any, int, error) {
+		if len(r.Header.Values("Idempotency-Key")) != 0 {
+			return nil, 0, fault.Invalid("batch requires per-item idempotency_key, not an Idempotency-Key header")
+		}
+		var in service.BatchSubmitInput
+		if err := decodeBody(r, &in); err != nil {
+			return nil, 0, err
+		}
+		out, err := s.SubmitBatch(r.Context(), t, in)
+		return out, http.StatusOK, err
+	}))
 	mux.HandleFunc("POST /v1/tasks", wrap(func(r *http.Request, t auth.Token) (any, int, error) {
 		var in service.SubmitInput
 		if err := decodeBody(r, &in); err != nil {