Basic backend flow for labs module

[khavinshankar]

The actuall progress of the labs module is tracked in ohcnetwork/care_fe#8683, this issue is only for tracking sprint progress.

• Specs and model for Service Request
• Use LOINC for lab orders
• Specs and model for Specimen
• Auto-create specimen based on the lab order code
• Convert LOINC specimen to SCT code
• Specs and model for Diagnostic Report
• Create flow-specific APIs (to update status changes like sent to lab and such, to add processes, to add observations, ...)