feat: manage epay settings securely

deploy/validate-staging-env.sh

@@ -97,6 +97,13 @@ if [[ "$LITERAL_VALUE" != *@* ]]; then
   echo "invalid staging identity setting: ADMIN_EMAILS" >&2
   exit 1
 fi
+require_literal EPAY_CONFIG_ENCRYPTION_KEY 44
+if [ "${#LITERAL_VALUE}" -ne 44 ] ||
+  [[ ! "$LITERAL_VALUE" =~ ^[A-Za-z0-9+/]{43}=$ ]]; then
+  echo "invalid staging identity setting: EPAY_CONFIG_ENCRYPTION_KEY" >&2
+  exit 1
+fi
+require_selector EPAY_CHAT_ENABLED false
 require_literal JYOTISH_DYNAMIC_RECTIFICATION_TOKEN 32
 
 echo "staging environment selectors: valid"