node-gmail-api | Sample project to show how to use the gmail API | Email library

As a college exercise, it would be a really fun experiment, so it definitely worth the time you want to put into it. However, once you want to add more features, the complexity will go up pretty fast.

Here are a couple of ideas you can think of:

• It's pretty clear that your system can't do more things than the capabilities exposed by the APIs of communication apps (e.g. you can't have notifications in gmail if the API doesn't have this capability).
• For that reason, you should carefully study the APIs and what functionalities they expose. They have public docs that you can check out: (Gmail API, Facebook Messanger API)
• Some of the apps you want to communicate with may not have an official API (e.g. WhatsApp) - those kinds of details you definitely want to know from the start.
• Based on the analysis of those APIs, you should lay out a list of requirements for your system, which can be extracted from all the APIs, for example: message notifications, file transfers, user profiles, etc.
• In this way, you know exactly what capabilities your system should have, and you don't end up implementing a feature that is available only in 1 API out of 4.
• Also, it would be a bit challenging to design your system from a user perspective, because the apps have different usage patterns - chat apps, where messages are coming in real-time, vs email, which is not real-time communication. That's just a detail anyway, the gist of your project is to play with those APIs.

Also, it may worth checking out the Gateway Aggergation Pattern, which is related to this project - you may want the user to send a message to multiple apps, by using a single request to your service.