Enhancements for Schema per tenant multi-tenancy support

[kdhrubo]

Currently for schema per tenant multi-tenancy the cache loads tables from all the schemas.
This means a lot of metadata taking up runtime memory.

Hence proposed design change is to request for a dummy schema - which has the same tables as the tenant tables. Only load the table info from dummy schema. During runtime the schema can be switched based on the following rule

1. Find tenant schema in JWT claim
2. Find tenant schema in header

Override with 2 if 1 is present.