Add available property to cert_handler (#96)

lib/charms/observability_libs/v1/cert_handler.py

@@ -67,7 +67,7 @@
 
 LIBID = "b5cd5cd580f3428fa5f59a8876dcbe6a"
 LIBAPI = 1
-LIBPATCH = 8
+LIBPATCH = 9
 
 VAULT_SECRET_LABEL = "cert-handler-private-vault"
 
@@ -391,30 +391,37 @@ def _migrate_vault(self):
 
     @property
     def enabled(self) -> bool:
-        """Boolean indicating whether the charm has a tls_certificates relation."""
+        """Boolean indicating whether the charm has a tls_certificates relation.
+
+        See also the `available` property.
+        """
         # We need to check for units as a temporary workaround because of https://bugs.launchpad.net/juju/+bug/2024583
         # This could in theory not work correctly on scale down to 0 but it is necessary for the moment.
 
-        if not self.charm.model.get_relation(self.certificates_relation_name):
+        if not self.relation:
             return False
 
-        if not self.charm.model.get_relation(
-            self.certificates_relation_name
-        ).units:  # pyright: ignore
+        if not self.relation.units:  # pyright: ignore
             return False
 
-        if not self.charm.model.get_relation(
-            self.certificates_relation_name
-        ).app:  # pyright: ignore
+        if not self.relation.app:  # pyright: ignore
             return False
 
-        if not self.charm.model.get_relation(
-            self.certificates_relation_name
-        ).data:  # pyright: ignore
+        if not self.relation.data:  # pyright: ignore
             return False
 
         return True
 
+    @property
+    def available(self) -> bool:
+        """Return True if all certs are available in relation data; False otherwise."""
+        return (
+            self.enabled
+            and self.server_cert is not None
+            and self.private_key is not None
+            and self.ca_cert is not None
+        )
+
     def _on_certificates_relation_joined(self, _) -> None:
         # this will only generate a csr if we don't have one already
         self._generate_csr()