This becomes a dictionary of key <lister-name>, value a dict of key
<instance-name>, value list of dict username/password.
This allows configuration change to allow the following:
credentials: github: # github lister github: # has only one instance (so far) - username: some password: somekey - username: one password: onekey - ... gitlab: # gitlab lister riseup: # has many instances - username: someone password: ... - ... gitlab: - username: someone password: ... - ...
Related T1772