[FEATURE]: Refactor digitalocean_database_firewall

[stawii]

Is there an existing issue for this?

• [X] I have searched the existing issues

Is your feature request related to a problem? Please describe

I cannot create rule for droplet.

Describe the solution you'd like

• rename var.firewall_rules to var_allowed_ip_addr
• add var.allowed_droplets_ids
• same for k8s, tags, apps

Describe alternatives you've considered

-

Anything else?

Check https://registry.terraform.io/providers/digitalocean/digitalocean/latest/docs/resources/database_firewall#type

[stawii]

Sync:

• https://github.com/opsd-io/terraform-module-digitalocean-postgresql/issues/6
• https://github.com/opsd-io/terraform-module-digitalocean-mysql/issues/5
• https://github.com/opsd-io/terraform-module-digitalocean-redis/issues/4