Fix JSON deserialize error that TrackLink::id could be null

[ramsayleung]

Description

Fix JSON deserialize error that TrackLink::id could be null, and add the missing type and uri field for TrackLink based on the updated Spotify document: https://developer.spotify.com/documentation/web-api/concepts/track-relinking

Motivation and Context

• TrackLink::id can be null #486

Dependencies

None

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How has this been tested?

• All CI jobs pass
• newly added unit test: test_null_id_in_track_link pass

Is this change properly documented?

Yes.