Using HTTPs in application vs reverse proxy
You will find people from both camps (terminating TLS as soon as possible vs terminating TLS in the application code) but it's not as serious as for example tabs vs spaces.

The benefit of terminating TLS by reverse proxy is that application developer does not have to implement TLS in the application itself - possibly introducing bugs. Another benefit mentioned by jdog is the CPU cost; which is negligible these days - unless you are running 100s of micro-services and it all adds up to a large chunk of money.

Personally I always go with reverse proxy terminating the TLS unless there is a specific requirement against it (security reasons). I also make sure that service behind reverse proxy listens on the localhost / local network only - is not accessible directly form the internet.

You may find wikipedia article about TLS termination useful.