Allow creation, removal, re-validation and retrieval of alerts that might get visible to Business Manager users.

The alerts have to be registered by the 'alerts.json' descriptor file in a cartridge assigned to the Business Manager site. The descriptor file itself has to be defined in 'package.json' of that cartridge using a property 'alerts' and providing its path that is relative to the 'package.json'. The 'alert.json' descriptor files contain the 'alert descriptions', which are referenced by their ID throughout the API.

For example, the 'alerts.json' file could have the following content:

 {
   "alerts": [
     {
       "alert-id": "missing_org_config",
       "menu-action": "global-prefs_custom_prefs",
       "message-resource-id": "global.missing_org_config",
       "priority": "ACTION",
       "remediation": {
         "pipeline":"GlobalCustomPreferences",
         "start-node":"View"
       }
     },
     {
       "alert-id":"promo_in_past",
       "menu-action":"marketing_promotions",
       "context-object-type":"Promotion",
       "message-resource-id":"promotion.in_the_past",
       "priority":"WARN",
       "remediation": {
         "pipeline":"ViewApplication",
         "start-node":"BM",
         "parameter":"screen=Promotion"
       }
     }
   ]
 }