Fix non-azure openai generation issues - part 1

[MaryGao]

this is part of the issue #2042 and fixes #2046.

• Support cutom http auth in Modular and enable auth testing in cadl-ranch
• Fix error response issue not from azure core
• Fallback to package name if no scope defined in package name
• Add a pipeline property in classical client to allow customizing policy

[MaryGao]

We can only change underlying policy in API layer and can't do this in classical layer. This is a breaking for mgmt SDK, I was wondering if we need to re-visit this design.

@qiaozha How do you think?

[qiaozha]

Based on our past experience when handling the customer issues for mgmt plane, we do recommend our customers to use customized policy for serveral times. Personally, I don't think it worth a breaking here to recommend them to custom it in the api layer.

If we want to have an exact same user experience like mgmt plane to use client.pipeline.addPolicy() and client.pipeline.removePolicy() , we have to add a new property in the classical client layer.
public pipeline: Pipeline; and change the constructor like

export class ApiKeyClient {
  private _client: ApiKeyContext;
  public pipeline: Pipeline;

  /** Illustrates clients generated with ApiKey authentication. */
  constructor(credential: KeyCredential, options: ApiKeyClientOptions = {}) {
    this._client = createApiKey(credential, options);
    this.pipeline = this._client.pipeline;
  }
  ...
}

Not sure if others have different opinions or have other options about it. @joheredi thoughts ?

[MaryGao]

I prefer to have a pipeline in classical client first and we could refactor these logic to core whenever necessary in future. @joheredi Not sure you have any concern?

[MaryGao]

updated in commit ab2632b

[qiaozha]

why not change the test into using the classical client layer pipeline ?

[MaryGao]

autorest.typescript/packages/typespec-ts/test/modularIntegration/authUnion.spec.ts

Line 77 in 6378211

describe("UnionClient in classical client", () => {

[MaryGao]

@joheredi I merged this pr but feel free to add any comment if you have!