Loopback - Extended AccessToken model not working - angularjs

Question

I'm using loopback's passport component with AngularJs frontend. I've created custom model for User as Person and for AccessToken as PersonAccessToken.
I'm able to login in correctly through facebook and redirect it to the angularjs client. But what I see is that access tokens are getting stored in built in AccessToken model rather than my custom PersonAccessToken model.
So when I call Person.logout() function it throws 500 server error since it cannot find any access tokens stored.
Person.json:
{
"name": "Person",
"base": "User",
"strict": false,
"idInjection": false,
"options": {
"validateUpsert": true
},
"properties": {},
"validations": [],
"relations": {
"hasCredentials": {
"type": "hasMany",
"model": "PersonCredential",
"foreignKey": "personId"
},
"hasIdentities": {
"type": "hasMany",
"model": "PersonIdentity",
"foreignKey": "personId"
},
"hasAccessToken": {
"type": "hasMany",
"model": "PersonAccessToken",
"foreignKey": "personId"
}
},
"acls": [
{
"accessType": "WRITE",
"principalType": "ROLE",
"principalId": "$owner",
"permission": "ALLOW"
},
{
"accessType": "READ",
"principalType": "ROLE",
"principalId": "$authenticated",
"permission": "ALLOW"
}
],
"methods": {}
}
PersonAccessToken.json:
{
"name": "PersonAccessToken",
"base": "AccessToken",
"strict": false,
"idInjection": false,
"options": {
"validateUpsert": true
},
"properties": {},
"validations": [],
"relations": {
"belongsToPerson": {
"type": "belongsTo",
"model": "Person",
"foreignKey": "personId"
}
},
"acls": [],
"methods": {}
}
model-config.json:
{
"_meta": {
"sources": [
"loopback/common/models",
"loopback/server/models",
"../common/models",
"./models",
"./node_modules/loopback-component-passport-c/lib/models"
],
"mixins": [
"loopback/common/mixins",
"loopback/server/mixins",
"../common/mixins",
"./mixins"
]
},
"User": {
"dataSource": "db",
"public": false
},
"AccessToken": {
"dataSource": "db",
"public": false
},
"ACL": {
"dataSource": "db",
"public": false
},
"RoleMapping": {
"dataSource": "db",
"public": false
},
"Role": {
"dataSource": "db",
"public": false
},
"Person": {
"dataSource": "db",
"public": true,
"$promise": {},
"$resolved": true
},
"PersonIdentity": {
"dataSource": "db",
"public": true,
"$promise": {},
"$resolved": true
},
"PersonCredential": {
"dataSource": "db",
"public": true,
"$promise": {},
"$resolved": true
},
"PersonAccessToken": {
"dataSource": "db",
"public": true,
"$promise": {},
"$resolved": true
}
}
datasources.json:
{
"db": {
"name": "db",
"connector": "memory",
"file": "db.json"
}
}
and in server.js I've included
boot(app, __dirname);
app.middleware('auth', loopback.token({
model: app.models.PersonAccessToken
}));
I don't know what I've been missing or doing wrong? Why is it not storing access tokens in my custom PersonAccessToken model?