title: Foreign-data wrapper "postgres_fdw" does not exist (even if it does)
body: <p>Using PostgreSQL 10.10, from superuser <code>postgres</code>:</p>
  
  <pre><code>CREATE EXTENSION postgres_fdw;
  GRANT USAGE ON FOREIGN DATA WRAPPER postgres_fdw TO my_user;
  </code></pre>
  
  <p>Then when doing the following from <code>my_user</code>:</p>
  
  <pre><code>CREATE SERVER my_server
  FOREIGN DATA WRAPPER postgres_fdw
  OPTIONS (...);
  </code></pre>
  
  <p>This error message is displayed:</p>
  
  <pre><code>Query 1 ERROR: ERROR:  foreign-data wrapper "postgres_fdw" does not exist
  </code></pre>
  
  <p>Here is the list of currently active foreign data wrappers (from psql):</p>
  
  <pre><code>postgres=# \dew
                        List of foreign-data wrappers
       Name     |  Owner   |       Handler        |       Validator
  --------------+----------+----------------------+------------------------
   postgres_fdw | postgres | postgres_fdw_handler | postgres_fdw_validator
  (1 row)
  </code></pre>
  
  <p>How comes, even after having been granted <code>USAGE</code>, the user <code>my_user</code> is still not able to see/use postgres_fdw foreign data wrapper, as if the latter didn't exist? Are there more steps necessary?</p>