Add an imagery blacklist to capabilities

This blacklist is for imagery which is of an incompatible license or ToS
but is incorrectly used with some frequency.

This adds a <policy> element to the capabilities XML which contains the
blacklist information within it

config/example.application.yml

@@ -84,6 +84,11 @@ defaults: &defaults
   require_terms_seen: false
   # Whether to require users to agree to the CTs before editing
   require_terms_agreed: false
+  # Imagery to return in capabilities as blacklisted
+  imagery_blacklist:
+    - ".*\\.googleapis\\.com/.*"
+    - ".*\\.google\\.com/.*"
+    - ".*\\.google\\.ru/.*"
 
 development:
   <<: *defaults