Alerting: Support WeCom as a contact point type (#40975)

* add wecom notifier

* fix backend lint

* fix alerting channel test

* update wecom doc

* update notifiers

* update wecom notifier test

* Apply suggestions from code review

Co-authored-by: gotjosh <josue.abreu@gmail.com>

* unify wecom alerting

* fix backend lint

* fix front lint

* fix wecom test

* update docs

* Update pkg/services/ngalert/notifier/channels/wecom.go

Co-authored-by: gotjosh <josue.abreu@gmail.com>

* Update docs/sources/alerting/old-alerting/notifications.md

Co-authored-by: gotjosh <josue.abreu@gmail.com>

* Update docs/sources/alerting/old-alerting/notifications.md

Co-authored-by: gotjosh <josue.abreu@gmail.com>

* Update docs/sources/alerting/old-alerting/notifications.md

Co-authored-by: gotjosh <josue.abreu@gmail.com>

* remove old wecom notifier

* remove old notifier doc

* fix backend test

* Update docs/sources/alerting/unified-alerting/contact-points.md

Co-authored-by: gotjosh <josue.abreu@gmail.com>

* fix doc style

Co-authored-by: gotjosh <josue.abreu@gmail.com>

pkg/tests/api/alerting/api_available_channel_test.go

@@ -1294,6 +1294,47 @@ var expAvailableChannelJsonOutput = `
       }
     ]
   },
+  {
+	"type": "wecom",
+	"name": "WeCom",
+	"heading": "WeCom settings",
+	"description": "Send alerts generated by Grafana to WeCom",
+	"info": "",
+	"options": [
+	  {
+		"element": "input",
+		"inputType": "text",
+		"label": "Url",
+		"description": "",
+		"placeholder": "https://qyapi.weixin.qq.com/cgi-bin/webhook/send?key=xxxxxxxx",
+		"propertyName": "url",
+		"selectOptions": null,
+		"showWhen": {
+		  "field": "",
+		  "is": ""
+        },
+		"required": true,
+		"validationRule": "",
+		"secure": true
+	  },
+      {
+		"element": "textarea",
+		"inputType": "",
+		"label": "Message",
+        "description": "Custom WeCom message. You can use template variables.",
+        "placeholder": "{{ template \"default.message\" . }}",
+        "propertyName": "message",
+        "selectOptions": null,
+        "showWhen": {
+          "field": "",
+          "is": ""
+        },
+        "required": false,
+        "validationRule": "",
+		"secure": false
+      }
+	]
+  },
   {
     "type": "prometheus-alertmanager",
     "name": "Alertmanager",