Alerting: Receivers API (read only endpoints) (#81751)

* Add single receiver method

* Add receiver permissions

* Add single/multi GET endpoints for receivers

* Remove stable tag from time intervals

See end of PR description here: https://github.com/grafana/grafana/pull/81672

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

@@ -2007,12 +2007,91 @@
         }
       }
     },
+    "/v1/notifications/receivers": {
+      "get": {
+        "tags": [
+          "notifications"
+        ],
+        "summary": "Get all receivers.",
+        "operationId": "RouteGetReceivers",
+        "parameters": [
+          {
+            "type": "array",
+            "items": {
+              "type": "string"
+            },
+            "name": "names",
+            "in": "query"
+          },
+          {
+            "type": "integer",
+            "format": "int64",
+            "name": "limit",
+            "in": "query"
+          },
+          {
+            "type": "integer",
+            "format": "int64",
+            "name": "offset",
+            "in": "query"
+          },
+          {
+            "type": "boolean",
+            "name": "decrypt",
+            "in": "query"
+          }
+        ],
+        "responses": {
+          "200": {
+            "$ref": "#/responses/GetReceiversResponse"
+          },
+          "403": {
+            "description": "PermissionDenied",
+            "schema": {
+              "$ref": "#/definitions/PermissionDenied"
+            }
+          }
+        }
+      }
+    },
+    "/v1/notifications/receivers/{Name}": {
+      "get": {
+        "tags": [
+          "notifications"
+        ],
+        "summary": "Get a receiver by name.",
+        "operationId": "RouteGetReceiver",
+        "parameters": [
+          {
+            "type": "string",
+            "name": "name",
+            "in": "path",
+            "required": true
+          },
+          {
+            "type": "boolean",
+            "name": "decrypt",
+            "in": "query"
+          }
+        ],
+        "responses": {
+          "200": {
+            "$ref": "#/responses/GetReceiverResponse"
+          },
+          "404": {
+            "description": "NotFound",
+            "schema": {
+              "$ref": "#/definitions/NotFound"
+            }
+          }
+        }
+      }
+    },
     "/v1/notifications/time-intervals": {
       "get": {
         "description": "Get all the time intervals",
         "tags": [
-          "notifications",
-          "stable"
+          "notifications"
         ],
         "operationId": "RouteNotificationsGetTimeIntervals",
         "responses": {
@@ -2031,8 +2110,7 @@
     "/v1/notifications/time-intervals/{name}": {
       "get": {
         "tags": [
-          "notifications",
-          "stable"
+          "notifications"
         ],
         "summary": "Get a time interval by name.",
         "operationId": "RouteNotificationsGetTimeInterval",
@@ -7994,7 +8072,6 @@
       }
     },
     "alertGroup": {
-      "description": "AlertGroup alert group",
       "type": "object",
       "required": [
         "alerts",
@@ -8019,6 +8096,7 @@
       "$ref": "#/definitions/alertGroup"
     },
     "alertGroups": {
+      "description": "AlertGroups alert groups",
       "type": "array",
       "items": {
         "$ref": "#/definitions/alertGroup"
@@ -8124,6 +8202,7 @@
       }
     },
     "gettableAlert": {
+      "description": "GettableAlert gettable alert",
       "type": "object",
       "required": [
         "labels",
@@ -8187,7 +8266,6 @@
       "$ref": "#/definitions/gettableAlerts"
     },
     "gettableSilence": {
-      "description": "GettableSilence gettable silence",
       "type": "object",
       "required": [
         "comment",
@@ -8244,6 +8322,7 @@
       "$ref": "#/definitions/gettableSilences"
     },
     "integration": {
+      "description": "Integration integration",
       "type": "object",
       "required": [
         "name",
@@ -8426,7 +8505,6 @@
       "$ref": "#/definitions/postableSilence"
     },
     "receiver": {
-      "description": "Receiver receiver",
       "type": "object",
       "required": [
         "active",
@@ -8557,6 +8635,21 @@
         "$ref": "#/definitions/GettableTimeIntervals"
       }
     },
+    "GetReceiverResponse": {
+      "description": "",
+      "schema": {
+        "$ref": "#/definitions/GettableApiReceiver"
+      }
+    },
+    "GetReceiversResponse": {
+      "description": "",
+      "schema": {
+        "type": "array",
+        "items": {
+          "$ref": "#/definitions/GettableApiReceiver"
+        }
+      }
+    },
     "GettableHistoricUserConfigs": {
       "description": "",
       "schema": {