Add check for Container Registry token on custom requests

[ShaunDonn]

Description

Added interface called IContainerRegistryTokenVerifier with method CheckIfContainerRegistryAccessIsEnabled. In OSS, the base implementation of this method returns nothing, so it will not impact the current control flow. In PaaS, we will add an implementation of CheckIfContainerRegistryAccessIsEnabled which checks whether or not ExternalMI has been configured. If it has, the method will just return, if not, it will throw a 400-level error with a message specifying that External MI is not configured, which is required for custom requests.

Related issues

Addresses work item #103457

Testing

• all unit and integration tests pass

FHIR Team Checklist

• Update the title of the PR to be succinct and less than 65 characters
• Add a milestone to the PR for the sprint that it is merged (i.e. add S47)
• Tag the PR with the type of update: Bug, Build, Dependencies, Enhancement, New-Feature or Documentation
• Tag the PR with Open source, Azure API for FHIR (CosmosDB or common code) or Azure Healthcare APIs (SQL or common code) to specify where this change is intended to be released.
• CI is green before merge
• Review squash-merge requirements

Semver Change (docs)

Patch|Skip|Feature|Breaking (reason)