Migrate Zuora config to `any_config`

Description

Migrate the Zuora config to ZuoraConfig powered by anyway_config gem.

We will do that in 2 steps:

  1. Introduce ZuoraConfig class and validate its settings in live environments.
  2. Migrate all occurrences of Settings.value(:zuora_* to ZuoraConfig.
Edited by Vitaly Slobodin