Adding cluster-issuer annotation for TLS provisioning

Through the usage of cert-manager, the charms will be able
request TLS certificates to protect the Kubernetes Ingress
endpoint that is exposed.

Note: Cert-manager must be configured ahead of time.

Change-Id: I7dacdb8dca2f78664c5604e509e2516ae6023d06
Signed-off-by: sousaedu <eduardo.sousa@canonical.com>
diff --git a/installers/charm/nbi/tests/test_charm.py b/installers/charm/nbi/tests/test_charm.py
index c4e857f..2b4ea0f 100644
--- a/installers/charm/nbi/tests/test_charm.py
+++ b/installers/charm/nbi/tests/test_charm.py
@@ -48,6 +48,7 @@
             "ingress_whitelist_source_range": "",
             "tls_secret_name": "",
             "site_url": "https://nbi.192.168.100.100.xip.io",
+            "cluster_issuer": "vault-issuer",
         }
         self.harness.update_config(self.config)