Use customized external MongoDB with Hono

[JouHouFin]

Eclipse Hono has some kind of support for MongoDB-based device registry: https://www.eclipse.org/hono/docs/admin-guide/mongodb-device-registry-config/

MongoDB support can be enabled in Helm charts, BUT find out how to e.g. :

• Use external MongoDB deployment: i.e. how to deploy hono without using Eclipse Hono Helm charts
  AND How to customize Eclipse Hono helm charts to use the external MongoDB instance
  (https://github.com/eclipse/packages/blob/2760401288f22048346287d12abf53bd3b12320c/charts/hono/values.yaml#L1210-L1245
  )
• Achieve persistent storage of data (i.e database is intact after bringing Hono deployment down and back up), May depend on Document lifecycle management of Azure persistent volumes common-issues#10