@UnstableApi
    public GrpcServiceBuilder exceptionHandler(GrpcExceptionHandlerFunction exceptionHandler) {
        requireNonNull(exceptionHandler, "exceptionHandler");
        checkState(exceptionMappingsBuilder == null,
                   "addExceptionMapping() and exceptionHandler() are mutually exclusive.");

        if (this.exceptionHandler == null) {
            this.exceptionHandler = exceptionHandler;
        } else {
            this.exceptionHandler = this.exceptionHandler.orElse(exceptionHandler);
        }
        return this;
    }
Sets the specified {@link GrpcExceptionHandlerFunction} that maps a {@link Throwable}
to a gRPC {@link Status}.

<p>Note that this method and {@link #addExceptionMapping(Class, Status)} are mutually exclusive.
grpc/src/main/java/com/linecorp/armeria/server/grpc/GrpcServiceBuilder.java