Fix `Role.isOwner()` to check both principalId and principalType.
This fixes a bug where users from different User model were treated
as owners as long as their user id was the same as owner's id.
Allow LoopBack applications to configure multiple User models and share
the same AccessToken model.
To enable this feature:
1) In your custom AccessToken model:
- add a new property "principalType" of type "string".
- configure the relation "belongsTo user" as polymorphic,
using "principalType" as the discriminator
2) In your User models:
- Configure the "hasMany accessTokens" relation as polymorphic,
using "principalType" as the discriminator
When creating custom Role and Principal instances, set your
User model's name as the value of "prinicipalType".
ebarault