Implement firebase auth to validate phone numbers

[WilliamDormer]

Here's the description: Google provides free sms messaging but only for the purpose of authenticating users. We want to use that functionality to verify that the phone numbers that people are using with the app are valid. There is already a branch of the flutter application for it that you can work on. Basically you just need to go through the steps outlined in the firebase/flutter documentation for using sms authentication, and try to implement it within the application. Once you figure out how it works, we need to determine if there is a way to then pass that verification information to our backend, and you will have to update the '/account/get_auth' endpoint to match the specs you need. There is a pretty detailed description of what the functoin needs to do in the typescript comment.

[WilliamDormer]

basic functionality is now there. Still needs to be tested and made more robust, but the essential functionality is done.