New creates a new Fitbit provider, and sets up important connection details.

ScopeActivity includes activity data and exercise log related features, such as steps, distance, calories burned, and active minutes.

ScopeHeartRate includes the continuous heart rate data and related analysis.

ScopeLocation includes the GPS and other location data.

ScopeNutrition includes calorie consumption and nutrition related features, such as food/water logging, goals, and plans.

ScopeProfile is the basic user information.

ScopeSettings includes user account and device settings, such as alarms.

ScopeSleep includes sleep logs and related sleep analysis.

ScopeSocial includes friend-related features, such as friend list, invitations, and leaderboard.

ScopeWeight includes weight and related information, such as body mass index, body fat percentage, and goals.

Provider is the implementation of `goth.Provider` for accessing Fitbit.

Session stores data during the auth process with Fitbit.