Add last request time metric for each subject which will denote when the app was last opened or last interaction since the notification requests are sent whenever the app is opened.
https://sentry.io/welcome/ is a very nice tool that takes this info from the logs and provides valuable insights.
Also they provide it for free for open source projects
Right now each request is scheduled as it is received but we can have some sort of time based caching that accumulates the requests and processes them all together (after some time or based on the number of entries) since the requests will probably come in bursts.
A nice one to use is CacheBuilder from Guava library
Right now, the tasks are scheduled even if the task with same token and subject id with exactly the same time already exists.
An alternative way to schedule should be included which is based on time and equality of notification.
If notifications are exactly the same and scheduled time is also the same, these should be ignored.
Create a Simple web app with UI for accessing notification details for each subject.
Probably should take project and subject info from MP after authenticating with the MP using authorization code or password grant type
At first this can just be basic auth with info of all participants available to everyone.