Prevent metadata caching

Add Apache .htaccess file to prevent browser caching of generated JSON
metadata when deployed to our infrastructure.

This is part of https://phabricator.wikimedia.org/T315643

Author: gbirke

public/.htaccess

@@ -0,0 +1,21 @@
+# Prevent caching of JSON generated by banner-screenshots
+# The JSON is our "serverless API" and must therefore not be cached
+# Code inspired by https://www.a2hosting.com/kb/developer-corner/apache-web-server/turning-off-caching-using-htaccess
+# 
+# This file will only work when hosted on an Apache web server, not in the dev environment
+<FilesMatch "(metadata_summary.json|metadata.json)$">
+    <IfModule mod_expires.c>
+        ExpiresActive Off
+    </IfModule>
+    <IfModule mod_headers.c>
+        FileETag None
+        Header unset ETag
+        Header unset Pragma
+        Header unset Cache-Control
+        Header unset Last-Modified
+        Header set Pragma "no-cache"
+        Header set Cache-Control "max-age=0, no-cache, no-store, must-revalidate"
+        Header set Expires "Thu, 1 Jan 1970 00:00:00 GMT"
+    </IfModule>
+</FilesMatch>
+