imapc: Check for auth failures when saving messages

First, don't even attempt an APPEND if we've already seen an auth failure.
Second, if APPEND does fail because of auth error, set the correct error to
storage.

src/lib-storage/index/imapc/imapc-save.c

@@ -66,6 +66,9 @@ int imapc_save_begin(struct mail_save_context *_ctx, struct istream *input)
 
 	i_assert(ctx->fd == -1);
 
+	if (imapc_storage_client_handle_auth_failure(ctx->mbox->storage->client))
+		return -1;
+
 	ctx->fd = imapc_client_create_temp_fd(ctx->mbox->storage->client->client,
 					      &path);
 	if (ctx->fd == -1) {
@@ -171,6 +174,8 @@ static void imapc_save_callback(const struct imapc_command_reply *reply,
 			imapc_save_appenduid(ctx->ctx, reply, &uid);
 		imapc_save_add_to_index(ctx->ctx, uid);
 		ctx->ret = 0;
+	} else if (imapc_storage_client_handle_auth_failure(ctx->ctx->mbox->storage->client)) {
+		ctx->ret = -1;
 	} else if (reply->state == IMAPC_COMMAND_STATE_NO) {
 		imapc_copy_error_from_reply(ctx->ctx->mbox->storage,
 					    MAIL_ERROR_PARAMS, reply);