[BUG] No setting available for Monitor max triggers

[gmfmi]

Describe the bug
The number of Triggers allowed by monitors should not be hardcoded.

When adding a Monitor that contains more than 10 Triggers, this error is returned :

{
  "error" : {
    "root_cause" : [
      {
        "type" : "illegal_argument_exception",
        "reason" : "Monitors can only support up to 10 triggers."
      }
    ],
    "type" : "illegal_argument_exception",
    "reason" : "Monitors can only support up to 10 triggers."
  },
  "status" : 400
}

I did not found any good reason to hardcode this value to "10". As an example, the total number of Monitor default value is set to 1000 but can be dynamically redefined.

Other plugins installed
(not useful)

To Reproduce
Steps to reproduce the behavior:

POST _opendistro/_alerting/monitors
{
  "type": "monitor",
  "schema_version": 3,
  "name": "Error",
  "enabled": true,
  "schedule": {
    "period": {
      "interval": 1,
      "unit": "MINUTES"
    }
  },
  "inputs": [
    {
      "search": {
        "indices": [
          "*"
        ],
        "query": {
          "size": 0,
          "query": {
            "match_all": {}
          }
        }
      }
    }
  ],
  "triggers": [
    {
      "name": "ID 1",
      "severity": "3",
      "condition": {
        "script": {
          "source": "return false",
          "lang": "painless"
        }
      }
    },
    {
      "name": "ID 2",
      "severity": "3",
      "condition": {
        "script": {
          "source": "return false",
          "lang": "painless"
        }
      }
    },
    {
      "name": "ID 3",
      "severity": "3",
      "condition": {
        "script": {
          "source": "return false",
          "lang": "painless"
        }
      }
    },
    {
      "name": "ID 4",
      "severity": "3",
      "condition": {
        "script": {
          "source": "return false",
          "lang": "painless"
        }
      }
    },
    {
      "name": "ID 5",
      "severity": "3",
      "condition": {
        "script": {
          "source": "return false",
          "lang": "painless"
        }
      }
    },
    {
      "name": "ID 6",
      "severity": "3",
      "condition": {
        "script": {
          "source": "return false",
          "lang": "painless"
        }
      }
    },
    {
      "name": "ID 7",
      "severity": "3",
      "condition": {
        "script": {
          "source": "return false",
          "lang": "painless"
        }
      }
    },
    {
      "name": "ID 8",
      "severity": "3",
      "condition": {
        "script": {
          "source": "return false",
          "lang": "painless"
        }
      }
    },
    {
      "name": "ID 9",
      "severity": "3",
      "condition": {
        "script": {
          "source": "return false",
          "lang": "painless"
        }
      }
    },
    {
      "name": "ID 10",
      "severity": "3",
      "condition": {
        "script": {
          "source": "return false",
          "lang": "painless"
        }
      }
    },
    {
      "name": "ID 11",
      "severity": "3",
      "condition": {
        "script": {
          "source": "return false",
          "lang": "painless"
        }
      }
    }
  ]
}

Expected behavior
Have a dedicated setting in the alerts section. As an example, it could look like: opendistro.alerting.monitor.max_triggers (to be consistant with the existing opendistro.alerting.monitor.max_monitors).
See https://opendistro.github.io/for-elasticsearch-docs/docs/alerting/settings/#alerting-settings.

Desktop:

• OS: MacOS
• Browser: Chrome
• Version: 92.0.4515.107

Additional context
I run the OpenDistro stack using Docker with image v1.13.2.

[gmfmi]

I take a look at the source code, here is a quick solution that should to the trick.

In the file /alerting/src/main/kotlin/com/amazon/opendistroforelasticsearch/alerting/settings/AlertingSettings.kt

Replace:

const val MONITOR_MAX_TRIGGERS = 10

By:

val MONITOR_MAX_TRIGGERS = Setting.intSetting(
    "opendistro.alerting.monitor.max_triggers",
    10,
    Setting.Property.NodeScope, Setting.Property.Dynamic
)