Make consumer group name different per environment

If a shared Kafka is used by multiple tenants than mod-searchs from different deployments are considered as a single group (hence all messages distributed between them).

Approach:

• Introduce a new ENV env variable to define deployment name - similar what mod-pubsub has. Note, it can be reused for https://issues.folio.org/browse/MSEARCH-95
• set consumer-group-id as $ENV-mod-search-events-group

Acceptance criteria:

• The code is implemented
• The new variable described in README.