Support namespaces/domains/multi-tenancy

[saig0]

In order to support different namespaces/domains (i.e. multi-tenancy), we need a way to store the data based on the namespace and be able to query by the namespace This can be useful to collect data from multiple environments (e.g. dev/stage/prod) by a single consumer, especially, for building a testing tool and running multiple test cases.

Each data entity (e.g. processes, process instances, jobs, etc.) contains a new field for the namespace.

The importer sets the namespace when reading exported records.

The GraphQL queries contain an optional field to filter by the namespace.

Related to/depends on camunda-community-hub/zeebe-hazelcast-exporter#132.