Convert voluptuous Schema + prescriptions class to pydantic models

[VannTen]

Problem statement

• The prescription schema can go out of sync with the various units Prescription class, resulting in problem like Generated prescription do not match the expected schema prescriptions-refresh-job#205
• Reducing code size and have better typing across the code base

Proposal description

Use pydantic models = The class definition is the schema defintion, with built-in validation

Alternatives

N/A

Acceptance Criteria

• Replace voluptuous and units class by pydantic models (Use pydantics models for prescriptions #2418)
• Adapt prescriptions-refresh-job to make use of the new classes and not manipulate raw yaml(Create yaml from Prescriptions object (instead of the other way around) prescriptions-refresh-job#209)

Optionally:

• Rework the prescription Schema, add versioning

/sig stack-guidance
/priority important-longterm
/triage accepted
(in sig stack-guidance 30/01/2023)

[KPostOffice]

Is this something that could be turned into jsonSchema or protobuf specification?

[VannTen]

Yes, see https://docs.pydantic.dev/usage/schema/