Implemented Team-wise Chat System

[amlannandy]

Description

This PR implemented a team-wise chatsystem in the backend and mobile application. The detailed changes can be found below, listed commit-wise.

Commit 1

• Started work on backend implementation
• Created Message db model

Commit 2

• Created a separator chatroom controller which has route for fetching messages of a team chatroom
• Added websocket support and created a 'send_message' event
• Backend implementation complete

Commit 3

• Mobile implementation started
• Implemented route for fetching chatroom messages

Commit 4

• Created ChatScreen
• Added socketio client package for recieving and emitting events
• Mobile implementation complete

Fixes #609

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

How Has This Been Tested?

Test Configuration:

• Android 10
• Realme 3 Pro
• Windows 10
• Postman

https://user-images.githubusercontent.com/45410599/123503718-478d7200-d672-11eb-8203-ad363a499a8a.mp4

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules

[amlannandy]

@Useful-Ad-1249 Hello. Could you please review this? As I also have to write unit tests for the endpoints created here in my next PR.