Allow tenants to own their own admin schema

[punktilious]

Is your feature request related to a problem? Please describe. For non Db2 solutions, we still install some common tables in the fhir_admin schema. It would be useful (particularly in development scenarios when sharing a DBaaS) for each tenant to own its own set of fhir_admin tables. Currently the fhir_admin schema name cannot be changed. It should be made variable, and also with the option of sharing the same fhirdata schema.

Describe the solution you'd like More options on where to locate the fhir_admin schema for non-Db2 databases.

Describe alternatives you've considered Require the user to create multiple databases. This has cost implications for some DBaaS solutions.

Acceptance Criteria

1. GIVEN [a precondition] AND [another precondition] WHEN [test step] AND [test step] THEN [verification step] AND [verification step]

Additional context Our Db2 schema uses table partitioning and role-based access control (RBAC) to support multiple tenants. To support least privilege best practices, the admin objects must be installed in their own schema and owned by a different user. This mechanism does not apply to the PostgreSQL implementation.

[lmsurpre]

This will be easier if we drop the db2 multi-tenant schema. But then, maybe we should just ditch the admin schema completely...