[jitsi-dev] Searching for Internal notifier

Hello everyone,
i am applying for gsoc for my first time and I want to implement creating
and voting on polls on jitsi. I am currently familiarizing myself with the
code base. During my readings, i found out about UIEvents
but i cannot find the actual implementation of these events. Can someone
please direct me to where the actual implementations of these events are.
Also, I would love to here your thoughts on whether the polls should be
stored on a database or the browser since my current knowledge about the
system suggest nothing of storing user data.