Merge pull request #90 from FriendsOfSymfony/docs-links

[WIP] Add reference targets for bundle docs

Author: dbu

doc/invalidation-introduction.rst

@@ -24,8 +24,15 @@ HTTP Caching Terminology
 
     Time to live (TTL)
         Maximum lifetime of some content. Expressed in either an expiry date
-        for the content (the `Expires:` header) or its maximum age (the
-        `max-age` and `s-maxage` cache control directives).
+        for the content (the ``Expires:`` header) or its maximum age (the
+        ``max-age`` and ``s-maxage`` cache control directives).
+
+    Invalidation
+        Invalidating a piece of content means telling the caching proxy to no
+        longer serve that content to clients. The proxy can choose to either
+        discard the content immediately, or do so when it is next requested.
+        On that next request, the proxy will fetch a fresh copy from the
+        application.
 
 What is Cache Invalidation?
 ---------------------------

doc/proxy-configuration.rst

@@ -1,3 +1,5 @@
+.. _proxy-configuration:
+
 Caching Proxy Configuration
 ===========================
 

doc/user-context.rst

@@ -1,3 +1,5 @@
+.. _user-context:
+
 Cache on User Context
 =====================
 

doc/varnish-configuration.rst

@@ -86,6 +86,8 @@ Varnish contains a `ban lurker`_ that crawls the content to eventually throw out
 
 .. _ban lurker: https://www.varnish-software.com/blog/ban-lurker
 
+.. _varnish_tagging:
+
 Tagging
 ~~~~~~~