Ensure accessibility is restricted to 256 hosts for Azure Redis Cache

Firewall rules are set to allow Azure Redis Cache access for a large number of IPs, this may lead to undetected unauthorized access.

In Azure Console -

1. Open the Azure Portal and go to Azure Cache for Redis.
2. Select the Redis Cache you wish to edit.
3. Under Settings, select Firewall.
4. Remove/edit rules where the start or end IP addresses are 0.0.0.0.
5. Save.

In Terraform -

1. For each azurerm_redis_cache resource, configure an azurerm_redis_firewall_rule.
2. Ensure that the azurerm_redis_firewall_rule resource has start_ip and end_ip explicitly defined and neither are 0.0.0.0.

References:
https://learn.microsoft.com/en-us/azure/azure-cache-for-redis/
https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/redis_cache
https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/redis_firewall_rule