title: how to authenticate to azure devops api with out using username or password or PAT tokken
body: <p>Scenario:-
  we've created an application that has to update a few details in the discussion field of the azure DevOps task.
  But the azure DevOps account that we want to access is the clients.
  They have provided access to that ADO for us</p>
  <p>But we want to update the task on ADO using the &quot;Azure-DevOps&quot; client library (python) which uses the rest API under the hood</p>
  <pre><code>https://github.com/microsoft/azure-devops-python-api
  https://docs.microsoft.com/en-us/rest/api/azure/devops/?view=azure-devops-rest-6.1
  </code></pre>
  <p>I know that we can achieve this using the PAT token</p>
  <p>But as the client is not ready to give the PAT token, we are exploring other ways to access the API
  The client is ready to give us APP-ID &amp; APP-Secret (he'll configure in AAD)
  or else he is also okay with a service account</p>
  <p>I don't know how to use the APP-ID &amp; APP-Secret Or a service account  to authenticate the API of ADO, could anyone share your views</p>
  <p>below is the code that I am using to authenticate with the PAT token</p>
  <pre><code>@Python
  personal_access_token = 'izpjkfptjl'
  organization_url = 'https://microsoftit.visualstudio.com/{organisation}/{project}'
  Credentials1 = BasicAuthentication('', personal_access_token)
  connection = Connection(base_url=organization_url, creds=credentials)
  work_client  = connection.clients.get_work_item_tracking_client()
  WI = work_client.get_work_item(3)
  </code></pre>
  <p>could you let me know how to if its possible, or else at least with userName &amp; password?.</p>
  <p>if I use userName &amp; password it's returning 401 authorized</p>
  <p>Questions-
  I want to communicate with the above ADO using
  App ID or APP secret Or
  service account
  if these 2 are not possible at lease by UserName password</p>