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/post.json

@@ -764,6 +764,9 @@
     "uid": {
      "description": "UID is the unique identifier of the contact point. The UID can be\nset by the user.",
      "example": "my_external_reference",
+     "maxLength": 40,
+     "minLength": 1,
+     "pattern": "^[a-zA-Z0-9\\-\\_]+$",
      "type": "string"
     }
    },
@@ -2663,6 +2666,9 @@
      "type": "string"
     },
     "uid": {
+     "maxLength": 40,
+     "minLength": 1,
+     "pattern": "^[a-zA-Z0-9-_]+$",
      "type": "string"
     },
     "updated": {