[Se] Define how to check for two backslide conditions

[mario-guerra]

Context

The TypeSpec team has a plan for converting existing Azure services to TypeSpec. The process involves manual refinement of TypeSpec files (TSPs), validation through human reviews, and various work items assigned to different teams for approval and automation. The primary goal is to ensure that the converted TypeSpec generates an OpenAPI specification functionally equivalent to the original, maintaining round-trip correctness.

Description

The TypeSpec team needs to create mechanisms to detect two specific backslide conditions:

1. When a service that was converted to TypeSpec reverts to using OpenAPI.
2. When the OpenAPI specification is manually modified after being generated from TypeSpec.

These checks are crucial to maintain the integrity of the conversion process and ensure that services remain compliant with TypeSpec standards. The checks may have performance implications and could require reliance on oversight committees if they prove too complex to automate.

[allenjzhang]

For #2, are you referring to the OAS spec being outside of the rest-api-specs repo? If they are inside of the repo, tsv will catch it (at least we greened RPSaaSMaster)