Serve public keys through webapp

Add a utility script which uses the public key served over HTTP
to encrypt the secret.

Change-Id: If0e4e4f8509518c8440814e8088a343489b5c553
diff --git a/tests/fixtures/config/single-tenant/main.yaml b/tests/fixtures/config/single-tenant/main.yaml
index a22ed5c..d9868fa 100644
--- a/tests/fixtures/config/single-tenant/main.yaml
+++ b/tests/fixtures/config/single-tenant/main.yaml
@@ -4,3 +4,5 @@
       gerrit:
         config-repos:
           - common-config
+        project-repos:
+          - org/project