tsp, support TCGC added endpoint together with user defined endpoint for one client

[haolingdong-msft]

Linik #2861 (comment)

Now for below TSP definition, TCGC will add an client endpoint with server url set to {endpoint} which means the endpoint is overridable. But currently we did a workaroud for this case to just remove the TCGC added {endpoint}. So it is not overridable. We should support in generated SDK to make it overridable.

@server(
  "http://{region}.azure.net", "",
  {
    region: string;
  }
)

More detailed design will be added later.

A more complex case can be below:
There could be multiple @server to define different endpoint url. tsp definition is like below:

@server(
  "{endpoint}/widget",
  "Contoso Widget APIs",
  {
    /** 
Supported Widget Services endpoints (protocol and hostname, for example:
https://westus.api.widget.contoso.com).
 */
    endpoint: string,
  }
)
@server(
  "http://localhost:3000", "test endpoint"
)
@service({})
namespace My.Service;

Multiple server url defined for one client. This may need a seperate issue.

[weidongxu-microsoft]

I guess in short term the priority would be the simple single server case in TypeSpec (but TCGC adds the endpoint), e.g.

@server(
  "http://{region}.azure.net", "",
  {
    region: string;
  }
)

Full support for multiple server in TypeSpec be a more complicated problem.

[haolingdong-msft]

I guess in short term the priority would be the simple single server case in TypeSpec (but TCGC adds the endpoint), e.g.

@server(
  "http://{region}.azure.net", "",
  {
    region: string;
  }
)

Full support for multiple server in TypeSpec be a more complicated problem.

Update the issue description. Thanks.