Convert Refactor for Missing External MI Case

[ShaunDonn]

Description

This PR addresses the issue of a user being unable to make a default template call unless they have the permissions/access token necessary for a custom template request configured. Default templates are currently stored in the code base, so no external permissions/tokens should be required to access these templates. This PR enables the use case for convert using default templates without external permissions/tokens configured by separating out the logic and dependency chains for custom and default template convert requests.

Related issues

Addresses issue #102114.

Testing

Unit tests were updated to align with the two use cases achieved by the updated logic. A FHIR server was also run locally and the control flow was verified for both a default and custom template request.

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)

[ms-teli]

Thanks for making the changes.