docs(README): Improving readme with some demos and more info (#394)

Co-authored-by: Remigiusz Samborski <rsamborski@users.noreply.github.com>
Co-authored-by: Victor Chudnovsky <vchudnov@google.com>

README.rst

@@ -69,23 +69,116 @@ Windows
     <your-env>\Scripts\pip.exe install google-cloud-compute
 
 
+Authentication and Authorization
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+This client library supports authentication via `Google Application Default Credentials`_
+, or by providing a JSON key file for a Service Account. See examples below.
+
+`Google Application Default Credentials`_ (ADC) is the recommended way to authorize and authenticate
+clients. Here is an example of a client using ADC to authenticate:
+
+.. code-block:: python
+
+    from google.cloud import compute_v1
+
+    networks_client = compute_v1.NetworksClient()
+    for network in networks_client.list(project='YOUR_PROJECT'):
+        print(network)
+
+
+You can use a file with credentials to authenticate and authorize, such as a JSON key
+file associated with a Google service account. You can create service account keys and
+download them using the Google Cloud Console. For more information, see
+`Creating and managing Service Account keys`_.
+
+The library used to create the credentials objects is ``google-auth``. This example uses
+the Networks Client, but the same steps apply to the other clients in this package.
+Example:
+
+.. code-block:: python
+
+    from google.oauth2 import service_account
+    from google.cloud import compute_v1
+
+    credentials = service_account.Credentials.from_service_account_file(
+        '/path/to/key.json')
+
+    networks_client = compute_v1.NetworksClient(credentials=credentials)
+    for network in networks_client.list(project='YOUR_PROJECT'):
+        print(network)
+
+
+When you don't want to store secrets on disk, you can create credentials
+from in-memory JSON and use the ``from_service_account_info`` method. You can also limit the use of
+your credentials only to specified scopes. For more information about OAuth 2.0 scopes for Google APIs,
+see `Scopes documentation page`_. Example:
+
+.. code-block:: python
+
+    import json
+
+    from google.oauth2 import service_account
+    from google.cloud import compute_v1
+
+    json_acct_info = json.loads(function_to_get_json_creds())
+    credentials = service_account.Credentials.from_service_account_info(
+        json_acct_info)
+
+    scoped_credentials = credentials.with_scopes(
+        ['https://www.googleapis.com/auth/cloud-platform'])
+
+    networks_client = compute_v1.NetworksClient(credentials=scoped_credentials)
+    for network in networks_client.list(project='YOUR_PROJECT'):
+        print(network)
+
+.. _Google Application Default Credentials: https://cloud.google.com/docs/authentication/production
+.. _Creating and managing Service Account keys: https://cloud.google.com/iam/docs/creating-managing-service-account-keys#creating
+.. _Scopes documentation page: https://developers.google.com/identity/protocols/oauth2/scopes
+
+Long Running Operations
+~~~~~~~~~~~~~~~~~~~~~~~
+Long-Running Operations (LROs), like the many ``insert()`` operations, can be handled using
+the ``ExtendedOperation`` object that is returned when the LRO is started.
+
+You can wait for the completion of an operation using its ``result()`` method. This method accepts
+a ``timeout`` argument, specifying how long you want your process to wait for completion of the
+operation (in seconds). When the call to ``result()`` times out, the operation is not automatically
+cancelled. At any time, you can check whether the operation is complete by using its ``done()`` method.
+
+A sample method to handle LROs featuring error and warning reporting can be found in the Python
+code samples repository: `GoogleCloudPlatform/python-docs-samples`_
+
+.. _GoogleCloudPlatform/python-docs-samples: https://github.com/GoogleCloudPlatform/python-docs-samples/blob/main/compute/client_library/snippets/operations/wait_for_extended_operation.py
+
+
+Code Samples
+~~~~~~~~~~~~
+You can find useful code samples that will demonstrate the usage of this library on `the
+Google Cloud samples page`_.
+
+.. _the Google Cloud samples page: https://cloud.google.com/docs/samples?language=python&product=computeengine
+
+
+
 PyCharm/JetBrains IDEs
 ~~~~~~~~~~~~~~~~~~~~~~
-Since the library has grown in size, the files it consists of have outgrown the [default size limit of ~2.5Mb](https://www.jetbrains.com/help/pycharm/file-idea-properties.html).
-As a result, the code completion in JetBrains products can fail to work with the classes from our library. To
-fix this, you need to update the `idea.max.intellisense.filesize` setting in custom properties
-(Help -> Edit custom properties...). Just add a line like `idea.max.intellisense.filesize = 10000` to change this
+This library has now grown in size past the `JetBrains default size limit of ~2.5Mb`_.
+As a result, code completion in JetBrains products can fail to work with the classes from our library. To
+fix this, you need to update the ``idea.max.intellisense.filesize`` setting in custom properties
+(Help -> Edit custom properties...). Just add the line ``idea.max.intellisense.filesize = 10000`` to change this
 limit to ~10Mb.
 
+.. _JetBrains default size limit of ~2.5Mb: https://www.jetbrains.com/help/pycharm/file-idea-properties.html
+
 Next Steps
 ~~~~~~~~~~
 
 -  Read the `Client Library Documentation`_ for Compute Engine API
-   API to see other available methods on the client.
+   to see other available methods on the client.
 -  Read the `Compute Engine API Product documentation`_ to learn
    more about the product and see How-to Guides.
 -  View this `README`_ to see the full list of Cloud
    APIs that we cover.
 
-.. _Compute Engine API Product documentation:  https://cloud.google.com/compute/
-.. _README: https://github.com/googleapis/google-cloud-python/blob/main/README.rst
+.. _Compute Engine API Product documentation:  https://cloud.google.com/compute/docs/api/libraries
+.. _README: https://github.com/googleapis/google-cloud-python/blob/main/README.rst