add noop handler for /superfeedr/* that just logs the request

for #18

app.yaml

@@ -71,6 +71,10 @@ handlers:
   script: redirect.app
   secure: always
 
+- url: /superfeedr/.*
+  script: superfeedr.app
+  secure: always
+
 - url: /wm/.+
   script: add_webmention.app
   secure: always

superfeedr.py

@@ -0,0 +1,29 @@
+"""Superfeedr callback handlers.
+
+Not really sure what this will be yet. Background:
+https://github.com/snarfed/bridgy-fed/issues/18#issuecomment-430731476
+https://documentation.superfeedr.com/publishers.html
+"""
+import logging
+
+import webapp2
+
+import appengine_config
+
+
+class SuperfeedrHandler(webapp2.RequestHandler):
+    """Superfeedr subscription callback handler.
+
+    https://documentation.superfeedr.com/publishers.html#subscription-callback
+    """
+
+    def post(self):
+        logging.info('Got:\n%s', self.request.body)
+        self.response.status_int = 204
+
+    get = post
+
+
+app = webapp2.WSGIApplication([
+    (r'/superfeedr/.*', SuperfeedrHandler),
+], debug=appengine_config.DEBUG)