Alerting: Remove the POST endpoint for the internal Grafana Alertmanager config (#103819)

* Remove POST config for Grafana Alertmanager

* Delete auth + test for removed path

* Alerting: Remove check for `alertingApiServer` toggle in UI (#103805)

* Remove check for alertingApiServer in UI

* Update tests to no longer care about alertingApiServer

* Add contact points handlers now that we use alertingApiServer all the time

* Fix test broken from removing camelCase for UIDs

---------

Co-authored-by: Tom Ratcliffe <tom.ratcliffe@grafana.com>

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

@@ -321,38 +321,6 @@
           }
         }
       },
-      "post": {
-        "description": "This API is designated to internal use only and can be removed or changed at any time without prior notice.",
-        "tags": [
-          "alertmanager"
-        ],
-        "summary": "sets an Alerting config",
-        "operationId": "RoutePostGrafanaAlertingConfig",
-        "deprecated": true,
-        "parameters": [
-          {
-            "name": "Body",
-            "in": "body",
-            "schema": {
-              "$ref": "#/definitions/PostableUserConfig"
-            }
-          }
-        ],
-        "responses": {
-          "201": {
-            "description": "Ack",
-            "schema": {
-              "$ref": "#/definitions/Ack"
-            }
-          },
-          "400": {
-            "description": "ValidationError",
-            "schema": {
-              "$ref": "#/definitions/ValidationError"
-            }
-          }
-        }
-      },
       "delete": {
         "description": "This API is designated to internal use only and can be removed or changed at any time without prior notice.",
         "tags": [