title: @UniqueConstraints not working on @JoinTable
body: <p>I'm using Playframework 1.2.4 and PostgresSQL 9.1.2. I have the following entities: Recipe and RecipeItem. A Recipe has a set of RecipeItems. I've annotated the set of recipe items in the Recipe class as follows:</p>
  
  <pre><code>@Required
  @MinSize(1)
  @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
  @JoinTable( name = "RecipeItemForIngredients",
  joinColumns = @JoinColumn(name = "recipeId"),
  inverseJoinColumns = @JoinColumn(name = "recipeItemId"),
  uniqueConstraints = @UniqueConstraint(name = "uq_recipeItemPerRecipe",
  columnNames = {"recipeId", "recipeItemId"}))
  public Set&lt;RecipeItem&gt; items = Sets.newHashSet();
  </code></pre>
  
  <p>But when I check the PgAdmin to see if the constraint has been applied to the RecipeItemForIngredients table I cannot find it. This is what PgAdmin shows.</p>
  
  <pre><code>CREATE TABLE recipeitemforingredients
  (
    recipeid bigint NOT NULL,
    recipeitemid bigint NOT NULL,
    CONSTRAINT recipeitemforingredients_pkey PRIMARY KEY (recipeid, recipeitemid),
    CONSTRAINT fk5ac547a883708db FOREIGN KEY (recipeid)
        REFERENCES recipe (id) MATCH SIMPLE
        ON UPDATE NO ACTION ON DELETE NO ACTION,
    CONSTRAINT fk5ac547ad6e1da8f FOREIGN KEY (recipeitemid)
        REFERENCES "recipe$recipeitem" (id) MATCH SIMPLE
        ON UPDATE NO ACTION ON DELETE NO ACTION,
    CONSTRAINT recipeitemforingredients_recipeitemid_key UNIQUE (recipeitemid)
  )
  </code></pre>
  
  <p>Does anyone have an idea why this could be happening? Maybe this annotation is not supported by the ORM used by Playframework.</p>