Alerting: Update provisioning to validate user-defined UID on create (#73793)

* add ValidateUID to util
* provisioning to validate UID on rule creation

---------

Co-authored-by: brendamuir <100768211+brendamuir@users.noreply.github.com>
Co-authored-by: Alexander Weaver <weaver.alex.d@gmail.com>

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

@@ -3625,6 +3625,9 @@
         "uid": {
           "description": "UID is the unique identifier of the contact point. The UID can be\nset by the user.",
           "type": "string",
+          "maxLength": 40,
+          "minLength": 1,
+          "pattern": "^[a-zA-Z0-9\\-\\_]+$",
           "example": "my_external_reference"
         }
       }
@@ -5534,7 +5537,10 @@
           "example": "Always firing"
         },
         "uid": {
-          "type": "string"
+          "type": "string",
+          "maxLength": 40,
+          "minLength": 1,
+          "pattern": "^[a-zA-Z0-9-_]+$"
         },
         "updated": {
           "type": "string",