doc: overall improvements

Created by: berendt

• update links in the documentation to point to the correct locations
• update the instructions for wireguard configuration to use the correct file name and clarify the purpose
• update the table of service URLs to remove unnecessary information andx fix formatting
• update the instructions for OpenStack CLI to clarify the command and environment selection
• update the instructions for importing additional images to include the export of OS_CLOUD variable
• update the troubleshooting section to clarify the steps for fixing broken disk setup
• update the rabbitmq_password to use a generic password instead of a specific one
• update the manager_listener_broker_password to use a generic password instead of a specific one