Refactor: link to db for stats page

[panadax]

Here is a basic link to the database:

1. I have created a database on Firebase, but only with some entities and attributes for the STATS page, please refer to here.
2. All the added code is still stored stats_fragment.kt, which I think is not good, also, I need to know more about the code architecture of our app folders to decide.
3. I know the code I wrote is messy, thank you for your patience in reviewing!
4. Next step: change the opponent id to name (I am a little into trouble with this, but due to limited time, I temporarily set it aside); spinner(selector) function design; match details page linking with DB as well.

[leonardopennino]

You should not hardcode it like that when we have a root collection. Hardcoding it like that makes it impossible to test with an ENV different than production.

[leonardopennino]

Almost good, resolve the issues I highlighted in your files and I'll approve it

[panadax]

For this sprint, I have refactored the function in FirebaseHelper, which should be compatible with Game and Round Class and Database. Please have a quick check :) Thank you.

[panadax]

Main issue checkpoint:

1. The logic in FirebaseHelper.kt
2. Should I use "viewLifecycleOwner.lifecycleScope.launch {}" to call the function in FirebaseHelper?

If the logic is correct and the code fulfilled the requirements, I will try to write the test :) I really appreciate your time to review my code!

[gaetschwartz]

Except these few issues, LGTM.