Add aqt connector (#246)

* Add AQT connector, OIDC auth

Author: jbrixon

docs/apidoc/provider.rst

@@ -4,11 +4,15 @@
 AQTProvider
 ===========
 
+
 .. autoclass:: qiskit_aqt_provider.aqt_provider.AQTProvider
    :members:
    :show-inheritance:
    :inherited-members:
 
+.. autoclass:: qiskit_aqt_provider.aqt_provider.ArnicaConfig
+   :members:
+
 .. autoclass:: qiskit_aqt_provider.aqt_provider.BackendsTable
    :members:
    :show-inheritance:

docs/guide.rst

@@ -19,6 +19,45 @@ Handles to computing resources are obtained through the :class:`AQTProvider <qis
 
 .. tip:: If no access token to the AQT cloud is available, the :class:`AQTProvider <qiskit_aqt_provider.aqt_provider.AQTProvider>` can nevertheless provide handles to direct-access resources and AQT-compatible simulators running on the local machine. This is the default behavior if the ``access_token`` argument to :meth:`AQTProvider <qiskit_aqt_provider.aqt_provider.AQTProvider.__init__>` is empty or invalid.
 
+
+Authentication with an Arnica account
+-------------------------------------
+.. tip:: Use this method if you were asked to create your own account to use the AQT Arnica portal.
+   
+Call :meth:`AQTProvider <qiskit_aqt_provider.aqt_provider.AQTProvider.__init__>` to log in and store your access token securely on the local machine.
+
+.. code-block::
+
+   from qiskit_aqt_provider import AQTProvider
+
+   provider = AQTProvider()
+   provider.log_in()
+
+
+Authentication with client credentials
+--------------------------------------
+.. tip:: Use this method if you received client credentials from AQT to use the Arnica portal.
+
+Use the `ArnicaConfig` helper class to configure the provider, then call :meth:`AQTProvider <qiskit_aqt_provider.aqt_provider.AQTProvider.__init__>` to exchange your credentials for an
+access token, which is stored on the local machine.
+
+.. code-block::
+
+   from qiskit_aqt_provider import AQTProvider
+   from qiskit_aqt_provider.aqt_provider import ArnicaConfig
+
+   config = ArnicaConfig(
+       client_id="YOUR_CLIENT_ID",
+       client_secret="YOUR_CLIENT_SECRET",
+   )
+   provider = AQTProvider(None, config)
+   provider.log_in()
+
+
+Authentication with a static API token
+--------------------------------------
+.. tip:: If you received an access token from AQT, you can use it to authenticate with the AQT cloud portal and access remote quantum computing resources.
+
 The access token can be configured by passing it as the first argument to the
 :class:`AQTProvider <qiskit_aqt_provider.aqt_provider.AQTProvider>` initializer: