fix: added validation to CBR input (#584)

Author: aamadeuss

README.md

@@ -98,7 +98,7 @@ To create service credentials, access the Event Notifications service, and acces
 | Name | Description | Type | Default | Required |
 |------|-------------|------|---------|:--------:|
 | <a name="input_access_tags"></a> [access\_tags](#input\_access\_tags) | A list of access tags to apply to the Event Notifications instance created by the module. [Learn more](https://cloud.ibm.com/docs/account?topic=account-access-tags-tutorial). | `list(string)` | `[]` | no |
-| <a name="input_cbr_rules"></a> [cbr\_rules](#input\_cbr\_rules) | The list of context-based restrictions rules to create. | <pre>list(object({<br/>    description = string<br/>    account_id  = string<br/>    rule_contexts = list(object({<br/>      attributes = optional(list(object({<br/>        name  = string<br/>        value = string<br/>    }))) }))<br/>    enforcement_mode = string<br/>    operations = optional(list(object({<br/>      api_types = list(object({<br/>        api_type_id = string<br/>      }))<br/>    })))<br/>  }))</pre> | `[]` | no |
+| <a name="input_cbr_rules"></a> [cbr\_rules](#input\_cbr\_rules) | The context-based restrictions rule to create. Only one rule is allowed. | <pre>list(object({<br/>    description = string<br/>    account_id  = string<br/>    rule_contexts = list(object({<br/>      attributes = optional(list(object({<br/>        name  = string<br/>        value = string<br/>    }))) }))<br/>    enforcement_mode = string<br/>    operations = optional(list(object({<br/>      api_types = list(object({<br/>        api_type_id = string<br/>      }))<br/>    })))<br/>  }))</pre> | `[]` | no |
 | <a name="input_cos_bucket_name"></a> [cos\_bucket\_name](#input\_cos\_bucket\_name) | The name of an existing IBM Cloud Object Storage bucket to use for storing failed delivery events. Required if `cos_integration_enabled` is set to `true`. | `string` | `null` | no |
 | <a name="input_cos_endpoint"></a> [cos\_endpoint](#input\_cos\_endpoint) | The endpoint URL for your bucket region. Required if `cos_integration_enabled` is set to `true`. [Learn more](https://cloud.ibm.com/docs/cloud-object-storage?topic=cloud-object-storage-endpoints). | `string` | `null` | no |
 | <a name="input_cos_instance_id"></a> [cos\_instance\_id](#input\_cos\_instance\_id) | The ID of an existing IBM Cloud Object Storage instance that contains the bucket to use for storing failed delivery events. Required if `cos_integration_enabled` is set to `true`. | `string` | `null` | no |

variables.tf

@@ -101,8 +101,12 @@ variable "cbr_rules" {
       }))
     })))
   }))
-  description = "The list of context-based restrictions rules to create."
+  description = "The context-based restrictions rule to create. Only one rule is allowed."
   default     = []
+  validation {
+    condition     = length(var.cbr_rules) <= 1
+    error_message = "Only one CBR rule is allowed."
+  }
 }
 
 variable "skip_en_kms_auth_policy" {