Alerting: send alerts to external, internal, or both alertmanagers (#40341)

* (WIP) send alerts to external, internal, or both alertmanagers

* Modify admin configuration endpoint, update swagger docs

* Integration test for admin config updated

* Code review changes

* Fix alertmanagers choice not changing bug, add unit test

* Add AlertmanagersChoice as enum in swagger, code review changes

* Fix API and tests errors

* Change enum from int to string, use 'SendAlertsTo' instead of 'AlertmanagerChoice' where necessary

* Fix tests to reflect last changes

* Keep senders running when alerts are handled just internally

* Check if any external AM has been discovered before sending alerts, update tests

* remove duplicate data from logs

* update comment

* represent alertmanagers choice as an int instead of a string

* default alertmanagers choice to all alertmanagers, test cases

* update definitions and generate spec

pkg/services/ngalert/api/tooling/post.json

@@ -769,6 +769,7 @@
       "Alerting"
      ],
      "type": "string",
+     "x-go-enum-desc": "Alerting AlertingErrState",
      "x-go-name": "ExecErrState"
     },
     "id": {
@@ -797,6 +798,7 @@
       "OK"
      ],
      "type": "string",
+     "x-go-enum-desc": "Alerting Alerting\nNoData NoData\nOK OK",
      "x-go-name": "NoDataState"
     },
     "orgId": {
@@ -838,6 +840,16 @@
      },
      "type": "array",
      "x-go-name": "Alertmanagers"
+    },
+    "alertmanagersChoice": {
+     "enum": [
+      "all",
+      "internal",
+      "external"
+     ],
+     "type": "string",
+     "x-go-enum-desc": "all AllAlertmanagers\ninternal InternalAlertmanager\nexternal ExternalAlertmanagers",
+     "x-go-name": "AlertmanagersChoice"
     }
    },
    "type": "object",
@@ -1718,6 +1730,7 @@
       "Alerting"
      ],
      "type": "string",
+     "x-go-enum-desc": "Alerting AlertingErrState",
      "x-go-name": "ExecErrState"
     },
     "no_data_state": {
@@ -1727,6 +1740,7 @@
       "OK"
      ],
      "type": "string",
+     "x-go-enum-desc": "Alerting Alerting\nNoData NoData\nOK OK",
      "x-go-name": "NoDataState"
     },
     "title": {
@@ -1749,6 +1763,16 @@
      },
      "type": "array",
      "x-go-name": "Alertmanagers"
+    },
+    "alertmanagersChoice": {
+     "enum": [
+      "all",
+      "internal",
+      "external"
+     ],
+     "type": "string",
+     "x-go-enum-desc": "all AllAlertmanagers\ninternal InternalAlertmanager\nexternal ExternalAlertmanagers",
+     "x-go-name": "AlertmanagersChoice"
     }
    },
    "type": "object",
@@ -2884,6 +2908,7 @@
    "x-go-package": "github.com/prometheus/alertmanager/api/v2/models"
   },
   "alertGroup": {
+   "description": "AlertGroup alert group",
    "properties": {
     "alerts": {
      "description": "alerts",
@@ -2905,16 +2930,15 @@
     "labels",
     "receiver"
    ],
-   "type": "object",
-   "x-go-name": "AlertGroup",
-   "x-go-package": "github.com/prometheus/alertmanager/api/v2/models"
+   "type": "object"
   },
   "alertGroups": {
-   "description": "AlertGroups alert groups",
    "items": {
     "$ref": "#/definitions/alertGroup"
    },
-   "type": "array"
+   "type": "array",
+   "x-go-name": "AlertGroups",
+   "x-go-package": "github.com/prometheus/alertmanager/api/v2/models"
   },
   "alertStatus": {
    "description": "AlertStatus alert status",
@@ -3096,13 +3120,15 @@
    "type": "object"
   },
   "gettableAlerts": {
-   "description": "GettableAlerts gettable alerts",
    "items": {
     "$ref": "#/definitions/gettableAlert"
    },
-   "type": "array"
+   "type": "array",
+   "x-go-name": "GettableAlerts",
+   "x-go-package": "github.com/prometheus/alertmanager/api/v2/models"
   },
   "gettableSilence": {
+   "description": "GettableSilence gettable silence",
    "properties": {
     "comment": {
      "description": "comment",
@@ -3154,9 +3180,7 @@
     "status",
     "updatedAt"
    ],
-   "type": "object",
-   "x-go-name": "GettableSilence",
-   "x-go-package": "github.com/prometheus/alertmanager/api/v2/models"
+   "type": "object"
   },
   "gettableSilences": {
    "description": "GettableSilences gettable silences",
@@ -3335,6 +3359,7 @@
    "type": "object"
   },
   "receiver": {
+   "description": "Receiver receiver",
    "properties": {
     "name": {
      "description": "name",
@@ -3345,9 +3370,7 @@
    "required": [
     "name"
    ],
-   "type": "object",
-   "x-go-name": "Receiver",
-   "x-go-package": "github.com/prometheus/alertmanager/api/v2/models"
+   "type": "object"
   },
   "silence": {
    "description": "Silence silence",
@@ -3456,8 +3479,8 @@
   }
  },
  "info": {
-  "description": "Package definitions includes the types required for generating or consuming an OpenAPI\nspec for the Grafana 8 Alerts API.",
-  "title": "Grafana 8 Alerts API.",
+  "description": "Package definitions includes the types required for generating or consuming an OpenAPI\nspec for the Grafana Alerting API.",
+  "title": "Grafana Alerting API.",
   "version": "1.1.0"
  },
  "paths": {
@@ -4400,7 +4423,7 @@
       }
      }
     },
-    "summary": "Creates or updates the NGalert configuration of the user's organization.",
+    "summary": "Creates or updates the NGalert configuration of the user's organization. If no value is sent for alertmanagersChoice, it defaults to \"all\".",
     "tags": [
      "configuration"
     ]