Add cloud-router configuration templates and scripts

- Introduced debian templates for cloud-router configuration parameters.
- Added simple-ca.sh script for managing a minimal Certificate Authority (CA) for IKEv2 PKI.
- Created sysctl configuration to enable IP forwarding and adjust rp_filter settings.
- Implemented configure script to render configuration files using Jinja2 templates.
- Added simple-ca script for generating CA and certificates.
- Created Jinja2 templates for various configuration files including netplan, strongSwan, and WireGuard.
- Implemented UFW rules setup for IPsec and WireGuard.
- Added support for road-warrior and site-to-site VPN configurations.

cloud-router-cloud-init.yaml.tpl

@@ -0,0 +1,28 @@
+#cloud-config
+
+apt:
+  sources:
+    cloud-router:
+      source: "deb [signed-by=/etc/apt/keyrings/cloud-router.gpg] ${repo_url} ${ubuntu_codename} main"
+      key: |
+        ${indent(8, trimspace(repo_gpg_key))}
+
+debconf_selections: |
+  cloud-router cloud-router/local_addrs           string   ${local_addrs}
+  cloud-router cloud-router/local_fqdn            string   ${fqdn}
+  cloud-router cloud-router/local_id_mode         select   ${local_id_mode}
+  cloud-router cloud-router/local_cidrs           string   ${local_cidrs}
+  cloud-router cloud-router/remote_addrs          string   ${remote_addrs}
+  cloud-router cloud-router/remote_id             string   ${remote_id}
+  cloud-router cloud-router/psk                   password ${psk}
+  cloud-router cloud-router/remote_cidrs          string   ${remote_cidrs}
+  cloud-router cloud-router/router_int_gateway_ip string   ${router_int_gateway_ip}
+  cloud-router cloud-router/p2s_address_pool      string   ${p2s_address_pool}
+  cloud-router cloud-router/wg_enabled            boolean  ${wg_enabled}
+  cloud-router cloud-router/wg_address            string   ${wg_address}
+  cloud-router cloud-router/wg_listen_port        string   ${wg_listen_port}
+
+package_update: true
+
+packages:
+  - cloud-router