Add Juju Public Key

This commit adds the requirement to provide the Juju public key to N2VC

- Updates integration testing to use public key
- Updates N2VC to accept juju_public_key and ca-cert
- Updated docstring of N2VC constructor

Change-Id: I4cad1f8c39024137a23060000d7502aad56ac644
Signed-off-by: Adam Israel <adam.israel@canonical.com>
diff --git a/tests/charms/layers/native-ci/metadata.yaml b/tests/charms/layers/native-ci/metadata.yaml
index 0460e48..ba6ffe9 100644
--- a/tests/charms/layers/native-ci/metadata.yaml
+++ b/tests/charms/layers/native-ci/metadata.yaml
@@ -4,9 +4,9 @@
 maintainer: Adam Israel <adam.israel@canonical.com>
 subordinate: false
 series: ['xenial']
-provides:
-    db:
-        interface: mysql
-requires:
-    app:
-        interface: mysql
+# provides:
+#     db:
+#         interface: mysql
+# requires:
+#     app:
+#         interface: mysql