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