Update `export` command to be flexible with HTTP/HTTPS ports

[abhishekkumams]

Currently, export command uses https endpoint but if it fails it will use http endpoint. but considering it's security implications we would like to add a cli option in the export command which will specify if we need to allow the use of fallback http url or not.

Add a cli option in export command.

Suggested Option:
--allow-http-fallback
Type: Boolean
Default Value: false
value required: No (acts like a switch)

example:
dab export --graphql -o ./schema --allow-http-fallback