add generateId config support in data handler

[championswimmer]

This will add support for the new feature added by @wolfgang42 here on jsonapi-server -
holidayextras/jsonapi-server#320

Signed-off-by: Arnav Gupta [email protected]

[championswimmer]

If you have to test it, change the dependency in package.json

"devDependencies": {
     ...
    "jsonapi-server": "github:wolfgang42/jsonapi-server#create-generate-id",
    ...
}