If an application developed to support only HTTP. What configuration we should do in google app engine, that it force developer to have HTTPS support. We can add an entry(for handler) in "app.yaml", but in order to redirection. Just want to know anything else we can do to prevent such thing(in short should work with HTTPS only). Probably we can do something from ingress/loadbalancer/ssl etc but that's looks paid and don't want that currently.
You just have to set secure: always in app.yaml for your route handlers. Any call to your app from http will automatically get redirected to https