Benki: Clean up the data model mapping some more.

 - Replaces user attribute table mappings with element collections and
   join table mappings.
 - Adds an explicit schema specifier to all join table specifiers.

Change-Id: I0e251e1939faa895155cbe868220d98be2c1e70c
diff --git a/src/main/java/eu/mulk/mulkcms2/benki/generic/Post.java b/src/main/java/eu/mulk/mulkcms2/benki/generic/Post.java
index a9a5ebd..309fb67 100644
--- a/src/main/java/eu/mulk/mulkcms2/benki/generic/Post.java
+++ b/src/main/java/eu/mulk/mulkcms2/benki/generic/Post.java
@@ -35,6 +35,7 @@
   @ManyToMany(fetch = FetchType.LAZY)
   @JoinTable(
       name = "user_visible_posts",
+      schema = "benki",
       joinColumns = @JoinColumn(name = "message"),
       inverseJoinColumns = @JoinColumn(name = "user"))
   public Set<User> visibleTo;