[Question/Feedback]: Adding Scope to Role Assignment Variable

### Check for previous/existing GitHub issues

- [x] I have checked for previous/existing GitHub issues

### Description

# Issue Statement: Adding Scope to Role Assignment Variable in AVM Data Protection Backup Vault Module

## Problem

When developing the Azure Data Protection Backup Vault module, linting fails because interfaces don't support the 'scope' attribute, which is needed to assign roles to external resources through the `role_assignments` variable.

```terraform
# Current variable definition lacks scope
variable "role_assignments" {
type = map(object({
role_definition_id_or_name = string
principal_id = string
description = optional(string, null)
# scope is missing
}))
}
```

## Critical Workflow Issue

Our backup workflow follows this sequence:
1. Resource Group is created with base Terraform
2. Module creates Backup Vault with Managed Identity
3. Module creates Backup Policy
4. **⚠️ Managed Identity needs permissions on Resource Group**
5. Backup instances are created using the policy

The module fails when trying to assign Resource Group permissions in step 4 because:
1. The identity doesn't exist until step 2 (can't create assignment before module)
2. The backup instance in step 4 requires permissions to be already established
3. The current module can't assign permissions outside the vault itself

## Impact

PostgreSQL Flexible Server backups consistently fail with `ProtectionError`:
```
Error: waiting for Backup Instance...unexpected state 'ProtectionError'
```

This occurs because the Backup Vault's identity needs Reader permissions on the Resource Group, but our module can't assign these permissions.

## Proposed Solution

Add `scope` to the `role_assignments` variable:

```terraform
variable "role_assignments" {
type = map(object({
role_definition_id_or_name = string
principal_id = string
description = optional(string, null)
# Other existing attributes...
scope = optional(string, null) # Add this
}))
}
```

This change aligns with Azure best practices and would fix PostgreSQL backup scenarios where Resource Group permissions are required for successful operation.