A generalised REST source connector:

Requests are generated by a request generator
A request generator can have multiple request routes (e.g. URL's), that are themselves request generators
A specialisation of a route is a polling route, that is expected to regularly poll a URL.
Use OkHttp3 for HTTP handling

Made a generalised Fitbit source connector:

Fitbit user registration is done outside of the connector, managed by a FitbitUserRepository.
- Its default implementation just reads and writes data from a directory using YAML files. It also refreshes any OAuth2 tokens when necessary.
With a FitbitRequestGenerator that has 4 routes:
1. intraday heart rate
2. intraday steps
3. sleep
4. time zone
Each of the routes is a FitbitPollingRoute, with a separate polling counter per Fitbit user. It features a full historical pull for the first iteration, after which only the most recent history is polled. If data is added more recently than before-yesterday, no new data is expected for earlier than before-yesterday. If no data was added since 14 days, earlier days are also not reinspected.
Data for each of the route is converted to Avro using RADAR Schemas.
The connector backs off for a given user if the server indicates that too many requests are being made.
Offsets are committed to the offset file, which is also read on startup.

Available under open source Apache License version 2.0