Support ManagedServiceIdentity from common-types

[XiaofeiCao]

Project Setup

Refer to https://github.com/Azure/cadl-ranch/blob/main/README.md for dev setup and PR prep.
Additionally: https://github.com/Azure/cadl-ranch/blob/main/packages/cadl-ranch-specs/README.md

managed-identity definition

https://github.com/Azure/typespec-azure/blob/fe90e201b7ad8bda7f98e786debfae37c025ee98/packages/typespec-azure-resource-manager/lib/common-types/managed-identity.tsp#L13

cadl-ranch-specs folder

put it under: http/azure/arm/models/common-types/managed-identity/main.tsp

usage

model Service is TrackedResource<ServiceProperties> {
  @doc("The name of Azure API Center service.")
  @maxLength(90)
  @minLength(1)
  @pattern("^[a-zA-Z0-9-]{3,90}$")
  @path
  @key("serviceName")
  @segment("services")
  name: string;

  ...ManagedServiceIdentityProperty;
}

https://github.com/Azure/azure-rest-api-specs/blob/44cbf51b9eee8a2dbf55ced61a61032aaed0148b/specification/apicenter/ApiCenter.Management/Service.tsp#L22

Test case

a simple PUT(createOrUpdate) and GET operation should suffice.
https://github.com/Azure/azure-rest-api-specs/blob/44cbf51b9eee8a2dbf55ced61a61032aaed0148b/specification/apicenter/ApiCenter.Management/Service.tsp#L27-L30

Candidate scenario:

1. Create Resource with SystemAssigned ManagedIdentity only
2. Update Resource with UserAssigned and SystemAssigned ManagedIdentity
3. Update Resource with UserAssigned ManagedIdentity only
4. Get Resource with UserAssigned and SystemAssigned ManagedIdentity

Example

PR for adding test case for TrackedResource, ProxyResource:
#588

main.tsp: https://github.com/Azure/cadl-ranch/blob/main/packages/cadl-ranch-specs/http/azure/arm/models/resources/main.tsp
(We only need one main.tsp for managed-identity, unlike resources, it has toplevel.tsp, etc)

mockapi.ts: https://github.com/Azure/cadl-ranch/blob/main/packages/cadl-ranch-specs/http/azure/arm/models/resources/mockapi.ts