Add default spam response

aardvark.yaml

diff --git a/aardvark.yaml b/aardvark.yaml
index fcd5c60..991fd49 100644
--- a/aardvark.yaml
+++ b/aardvark.yaml
@@ -7,6 +7,9 @@
 # Default IP forward header from httpd
 ipheader: x-forwarded-for
 
+# This is the text of the 403 response if a request is blocked
+spam_response: "Your request has been blocked. If you feel this is in error, please let us know at: abuse@infra.apache.org"
+
 # Debug prints for ...debug. disabled by default
 debug: false