Docs: Rename Message templates to Notification templates (#59477)

This commit renames "Message templates" to "Notification templates"
in the user interface as it suggests that these templates cannot
be used to template anything other than the message. However, message
templates are much more general and can be used to template other fields
too such as the subject of an email, or the title of a Slack message.

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

@@ -2276,13 +2276,13 @@
           "provisioning",
           "stable"
         ],
-        "summary": "Get all message templates.",
+        "summary": "Get all notification templates.",
         "operationId": "RouteGetTemplates",
         "responses": {
           "200": {
-            "description": "MessageTemplates",
+            "description": "NotificationTemplates",
             "schema": {
-              "$ref": "#/definitions/MessageTemplates"
+              "$ref": "#/definitions/NotificationTemplates"
             }
           },
           "404": {
@@ -2297,7 +2297,7 @@
           "provisioning",
           "stable"
         ],
-        "summary": "Get a message template.",
+        "summary": "Get a notification template.",
         "operationId": "RouteGetTemplate",
         "parameters": [
           {
@@ -2310,9 +2310,9 @@
         ],
         "responses": {
           "200": {
-            "description": "MessageTemplate",
+            "description": "NotificationTemplate",
             "schema": {
-              "$ref": "#/definitions/MessageTemplate"
+              "$ref": "#/definitions/NotificationTemplate"
             }
           },
           "404": {
@@ -2328,7 +2328,7 @@
           "provisioning",
           "stable"
         ],
-        "summary": "Updates an existing template.",
+        "summary": "Updates an existing notification template.",
         "operationId": "RoutePutTemplate",
         "parameters": [
           {
@@ -2342,15 +2342,15 @@
             "name": "Body",
             "in": "body",
             "schema": {
-              "$ref": "#/definitions/MessageTemplateContent"
+              "$ref": "#/definitions/NotificationTemplateContent"
             }
           }
         ],
         "responses": {
           "202": {
-            "description": "MessageTemplate",
+            "description": "NotificationTemplate",
             "schema": {
-              "$ref": "#/definitions/MessageTemplate"
+              "$ref": "#/definitions/NotificationTemplate"
             }
           },
           "400": {
@@ -3977,34 +3977,6 @@
       },
       "$ref": "#/definitions/Matchers"
     },
-    "MessageTemplate": {
-      "type": "object",
-      "properties": {
-        "name": {
-          "type": "string"
-        },
-        "provenance": {
-          "$ref": "#/definitions/Provenance"
-        },
-        "template": {
-          "type": "string"
-        }
-      }
-    },
-    "MessageTemplateContent": {
-      "type": "object",
-      "properties": {
-        "template": {
-          "type": "string"
-        }
-      }
-    },
-    "MessageTemplates": {
-      "type": "array",
-      "items": {
-        "$ref": "#/definitions/MessageTemplate"
-      }
-    },
     "MultiStatus": {
       "type": "object"
     },
@@ -4066,6 +4038,34 @@
       "format": "int64",
       "title": "NoticeSeverity is a type for the Severity property of a Notice."
     },
+    "NotificationTemplate": {
+      "type": "object",
+      "properties": {
+        "name": {
+          "type": "string"
+        },
+        "provenance": {
+          "$ref": "#/definitions/Provenance"
+        },
+        "template": {
+          "type": "string"
+        }
+      }
+    },
+    "NotificationTemplateContent": {
+      "type": "object",
+      "properties": {
+        "template": {
+          "type": "string"
+        }
+      }
+    },
+    "NotificationTemplates": {
+      "type": "array",
+      "items": {
+        "$ref": "#/definitions/NotificationTemplate"
+      }
+    },
     "NotifierConfig": {
       "type": "object",
       "title": "NotifierConfig contains base options common across all notifier configurations.",
@@ -5943,6 +5943,7 @@
       }
     },
     "gettableAlert": {
+      "description": "GettableAlert gettable alert",
       "type": "object",
       "required": [
         "labels",
@@ -5999,7 +6000,6 @@
       "$ref": "#/definitions/gettableAlert"
     },
     "gettableAlerts": {
-      "description": "GettableAlerts gettable alerts",
       "type": "array",
       "items": {
         "$ref": "#/definitions/gettableAlert"
@@ -6246,7 +6246,6 @@
       "$ref": "#/definitions/postableSilence"
     },
     "receiver": {
-      "description": "Receiver receiver",
       "type": "object",
       "required": [
         "active",