fix: pre-hotreload cartridge support

`crud` module is cartridge-independent in nature, but provides cartridge
roles which are the most popular way to setup the module. The roles also
not use any modern cartridge features and should work with any cartridge
version. But since crud.cfg was introduced [1], it was required to add
some code for roles reload [2] proper support. Now
cartridge.hotreload module is unconditionally required, so roles cannot
be used with cartridge older than 2.4.0. This patch fixes the behavior.

1. 6da4f56
2. tarantool/cartridge@941952e

Follows #244

Author: DifferentialOrange

CHANGELOG.md

@@ -5,6 +5,11 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Fixed
+* Pre-hotreload `cartridge` support (older than 2.4.0) (PR #341).
+
 ## [1.0.0] - 02-02-23
 
 ### Added

crud/common/stash.lua

@@ -2,6 +2,7 @@
 -- @module crud.common.stash
 --
 local dev_checks = require('crud.common.dev_checks')
+local utils = require('crud.common.utils')
 
 local stash = {}
 
@@ -37,7 +38,11 @@ stash.name = {
 -- @return Returns
 --
 function stash.setup_cartridge_reload()
-    local hotreload = require('cartridge.hotreload')
+    local hotreload_supported, hotreload = utils.is_cartridge_hotreload_supported()
+    if not hotreload_supported then
+        return
+    end
+
     for _, name in pairs(stash.name) do
         hotreload.whitelist_globals({ name })
     end

crud/common/utils.lua

@@ -6,6 +6,7 @@ local bit = require('bit')
 local log = require('log')
 
 local is_cartridge, cartridge = pcall(require, 'cartridge')
+local is_cartridge_hotreload, cartridge_hotreload = pcall(require, 'cartridge.hotreload')
 
 local const = require('crud.common.const')
 local schema = require('crud.common.schema')
@@ -963,4 +964,19 @@ function utils.get_vshard_router_instance(router)
     return router_instance
 end
 
+--- Check if Tarantool Cartridge hotreload supported
+--  and get its implementaion.
+--
+-- @function is_cartridge_hotreload_supported
+--
+-- @return[1] true or false
+-- @return[1] module table, if supported
+function utils.is_cartridge_hotreload_supported()
+    if not is_cartridge_hotreload then
+        return false
+    end
+
+    return true, cartridge_hotreload
+end
+
 return utils