To have different footer per instance the
content of the footer is now configurable
from the theme customization file.
See THEME_CUSTOMIZATION_FILE_PATH env var.
We want to customize the theme by using a configuration file. This
configuration file path can be defined using the settings
THEME_CUSTOMIZATION_FILE_PATH. If this file does not exists or is an
invalid json, an empty json object will be added in the config endpoint.