This class provides the credentials that we need to authenticate against Vault
and the credentials stored in Vault, after assigning the right context to them.
Requires either CASC_VAULT_USER and CASC_VAULT_PW, or CASC_VAULT_TOKEN, or CASC_VAULT_APPROLE and
CASC_VAULT_APPROLE_SECRET, or CASC_VAULT_KUBERNETES_ROLE, or CASC_VAULT_AWS_IAM_ROLE environment
variables set alongside with CASC_VAULT_PATHS and CASC_VAULT_URL