belongs_to preload issue

[rjgonzale]

Description

Add primary_id tag to belongs_to association when using EagerPreload

1 -
Right now if you are not using preload you can define the primary key field name when using belongs_to

But, if you use preload, it is hardcoded to be id

The code to change this can be (please excuse me that I am not to buffalo)

diff --git a/preload_associations.go b/preload_associations.go
index 5d3be99..7fa2b68 100644
--- a/preload_associations.go
+++ b/preload_associations.go
@@ -358,7 +358,10 @@ func preloadBelongsTo(tx *Connection, asoc *AssociationMetaInfo, mmi *ModelMetaI
        }

        // 2) load all associations constraint by association fields ids.
-       fk := "id"
+       fk := asoc.Field.Tag.Get("primary_id")
+        if fk == "" {
+                fk = "id"
+        }