Update container MOTD to include port forwards and services via API

[runleveldev]

Feature Overview

Add an API endpoint to provide up-to-date MOTD (Message of the Day) content for containers, including information about their port forwards and active services. The MOTD content should be tailored based on the requester's source IP.

Solution Details

• Implement an API endpoint in the container management service, such as /containers/:id/motd or /motd.
• The endpoint returns dynamically generated MOTD content with:
  • Port forwards relevant to the requesting container and IP address
  • List of exposed or running services per container
  • Any contextual information based on the request source IP
• Add a script to /etc/update-motd.d/ inside containers that pulls the MOTD from the new endpoint and updates the container's MOTD file.

Acceptance Criteria

• API endpoint exists and returns accurate MOTD content for containers and their source IP
• /etc/update-motd.d/ includes a script to fetch and update MOTD periodically or on demand
• Documentation for using the endpoint and integrating with container MOTD

Additional Notes

• The endpoint should be secure and expose no sensitive data
• Consider caching or limiting frequency to avoid excessive API calls

[runleveldev]

Dependent on #80 as it involves modifying the container template.

[runleveldev]

Intended to replace

opensource-server/container-creation/intern-phxdc-pve1/var-lib-vz-snippets/create-container-new.sh

Lines 295 to 320 in 22c8b3a

	echo "Adding container MOTD information..."
	# port_map.json remains on central nginx host (10.15.20.69) — leave as-is unless you want to change that behavior
	scp 10.15.20.69:/etc/nginx/port_map.json /tmp/port_map.json
	CONTAINER_INFO=$(jq -r --arg hn "$CONTAINER_NAME" '.[$hn]' /tmp/port_map.json)
	if [ "$CONTAINER_INFO" != "null" ]; then
	HOSTNAME="$CONTAINER_NAME"
	IP=$(echo "$CONTAINER_INFO" | jq -r '.ip')
	OWNER=$(echo "$CONTAINER_INFO" | jq -r '.user')
	OS_RELEASE=$(echo "$CONTAINER_INFO" | jq -r '.os_release')
	PORTS=$(echo "$CONTAINER_INFO" | jq -r '.ports | to_entries[] | "\(.key): \(.value)"' | paste -sd ", " -)
	PROTOCOLS=$(echo "$CONTAINER_INFO" | jq -r '.ports | keys | join(", ")')
	cat <<EOF > /tmp/container_motd
	Container Information:
	----------------------
	Hostname : $HOSTNAME
	IP Address : $IP
	Ports : $PORTS
	Protocols : $PROTOCOLS
	Primary Owner : $OWNER
	OS Release : $OS_RELEASE
	EOF
	else
	echo "No container info found for $CONTAINER_NAME" > /tmp/container_motd
	fi