Healthcheck operation should contact blob service when payload offload is enabled

[punktilious]

Is your feature request related to a problem? Please describe. When payload offload is configured, the $healthcheck operation should verify the blob service connection as well as the RDBMS connection.

Describe the solution you'd like As described.

Describe alternatives you've considered Accept the weaker check as currently implemented.

Acceptance Criteria

1. GIVEN a FHIR server configured with payload offloading WHEN a client calls the $healthcheck operation AND the blob service is unavailable THEN the healthcheck operation should return an error

Additional context N/A