Add config key oidc-client-id

The client id is part of the configuration information that the operator
is expected to hand over to the charm since it's part of the client's
auth configuration.

config.yaml

@@ -1,4 +1,9 @@
 options:
+  oidc-client-id:
+    default: ''
+    type: string
+    description: |
+      Client identifier.
   oidc-provider-metadata-url:
     default: ''
     type: string

src/charm.py

@@ -23,9 +23,8 @@ from typing import List
 from uuid import uuid4
 
 from ops.main import main
-from ops.model import StatusBase, ActiveStatus
+from ops.model import StatusBase, ActiveStatus, BlockedStatus
 
-import ops.model
 import ops_openstack.core
 
 from ops_openstack.adapters import (
@@ -216,8 +215,11 @@ class KeystoneOpenIDCCharm(ops_openstack.core.OSBaseCharm):
         return {'apache2': self.request_restart}
 
     def is_data_ready(self):
+        if not self.model.get_relation('cluster'):
+            return False
+
         options = KeystoneOpenIDCOptions(self)
-        required_keys = ['oidc_crypto_passphrase']
+        required_keys = ['oidc_crypto_passphrase', 'oidc_client_id']
         for key in required_keys:
             if getattr(options, key) == None:  # noqa: E711
                 return False