Wondering if there is an easier way to automate my newsletter and login?

I run a music discovery newsletter called What's Spinning (https://whats-spinning.life).
I created it as a way for users to track changes to Spotify playlists that they follow. For example, if you follow a lot of playlists on Spotify, there's not really a way to get notifications for when new songs are added. This newsletter aims to bridge that gap by sending subscribers a weekly digest of songs added to playlists they follow (as well as some curated music content like interesting album art, music news related to artists they follow, etc).

I am looking for product recommendations for a few use cases.

First, for my site, I require users to login with Spotify and then it grabs all the playlists they follow. From there, users can select playlists to "track". I am looking for a website host (currently using wordpress, but not in love with it) that allows custom API use so that I can rebuild the form to allow users to login with Spotify. Or instead of a website, some sort of form that allows custom API integration?

Second, I am dynamically building each person's email through python (I grab the most recent playlist changes, input some music news, album art) and send it through the sendgrid API. I am wondering if there are any newsletter host websites that allow you to host python code so I can run this through their site instead of locally?

Thank you!