Fix various Hibernate mapping oversights.

Change-Id: Iff22c68a718d6f65734e166cd08f4049ccc196ec
diff --git a/src/main/java/eu/mulk/mulkcms2/benki/posts/Post.java b/src/main/java/eu/mulk/mulkcms2/benki/posts/Post.java
index 0350a20..20fcabe 100644
--- a/src/main/java/eu/mulk/mulkcms2/benki/posts/Post.java
+++ b/src/main/java/eu/mulk/mulkcms2/benki/posts/Post.java
@@ -73,7 +73,7 @@
   @CheckForNull
   public OffsetDateTime date;
 
-  @Column(nullable = false)
+  @Column(nullable = false, columnDefinition = "benki.post_scope")
   @Enumerated(EnumType.STRING)
   @Type(PostgreSQLEnumType.class)
   public Scope scope = Scope.top_level;