Id that are Number should update with an Id as a string

[narf]

Tested with beta 3

This cause inconsistensy with my Db where ids are Numbers, all insert requests with belongsTo don't pass the validation process (the ref must be a number but ember cast it to a string).

I can understand that you need internally to play with strings, but why not keeping the base type for all queries? There is propably a way to do this like defining the type of the belongsTo, or maybe the type of the primary key for you to cast it before querying...

line 1174:

// Implementors Note:
//
//   The variables in this file are consistently named according to the following
//   scheme:
//
//   * +id+ means an identifier managed by an external source, provided inside
//     the data provided by that source. These are always coerced to be strings
//     before being used internally.
//   * +clientId+ means a transient numerical identifier generated at runtime by
//     the data store. It is important primarily because newly created objects may
//     not yet have an externally generated id.
//   * +reference+ means a record reference object, which holds metadata about a
//     record, even if it has not yet been fully materialized.
//   * +type+ means a subclass of DS.Model.

// Used by the store to normalize IDs entering the store.  Despite the fact
// that developers may provide IDs as numbers (e.g., `store.find(Person, 1)`),
// it is important that internally we use strings, since IDs may be serialized
// and lose type information.  For example, Ember's router may put a record's
// ID into the URL, and if we later try to deserialize that URL and find the
// corresponding record, we will not know if it is a string or a number.
var coerceId = function(id) {
  return id == null ? null : id+'';
};

[igorT]

You could override serializeBelongsTo to cast the strings as numbers. I think there should probably be an easier hook to handle this but not sure how exactly it should look: whether it should only be a one hook for both primaryKey and relationships.

[igorT]

Closing as a duplicate of #3078