Description of the feature request
Allow the environment variable set by the fastlane step for the api key to be customized by name.
Use case / for what or how I would use it
Currently the API key is exported as DELIVER_API_KEY_PATH. This only allows the fastlane step to run the deliver action of fastlane and no other actions. The environment variable cannot be used in the fastlane step due to the way Bitrise performs variable substitution. Would like to use the fastlane step to perform pilot actions.