how to migrate from AAP 2.4 to 2.5 / controller_configuration to aap_configuration

[djdanielsson]

this issue is to help track how to migrate from AAP 2.4 to 2.5 / controller_configuration to aap_configuration. more info to come soon, once all the major changes have been completed.

[David-Igou]

Usage of environment variables in general should be added to the general documentation or the conversion guide. Previously, the only requirements were CONTROLLER_HOST, CONTROLLER_USERNAME, CONTROLLER_PASSWORD (or CONTROLLER_TOKEN) but now those need to be set plus GATEWAY_HOSTNAME, GATEWAY_USERNAME, GATEWAY_PASSWORD

It's also worth questioning if the collection should expect a universal AAP_{HOST,USER,PASSWORD} environment variable, but that's probably a separate feature request