Deprecation Errors - How to Fix? We are in development of our new site in Craft 3 and we are getting some deprecation errors. This is keeping us from using Craft Commerce for our ordering page. Any suggestions on how to fix this?

Message Origin  Last Occurrence Stack Trace 
The Purchasable::getPurchasableId() function has been deprecated. Use Purchasable::getId() instead. /srv/captioncall/templates/buy/index.twig:6 Yesterday   Stack Trace 
craft.session.getFlash() has been deprecated. Use craft.app.session.getFlash() instead. /srv/captioncall/templates/buy/index.twig:33    Yesterday   Stack Trace 
craft.session.getFlash() has been deprecated. Use craft.app.session.getFlash() instead. /srv/captioncall/templates/buy/index.twig:34    Yesterday   Stack Trace
I'm not sure I can tell you much more than the error messages are telling you, you need to update your twig code eg. in index.twig (line 6) where it says; getPurchasableId() change it to getId().

These errors are just warning you that a future version of Craft won't support them (I imagine it will be Craft 4, but could be sooner).

Changing e-commerce systems based on this error would not be advised as it's a very simple fix!