Refactor NestBot app home section and commands code

[arkid15r]

Is your feature request related to a problem? Please describe.
Currently we have some code duplication for NestBot app home page actions and commands, e.g. 1 and 2, or 3 and 4

Describe the solution you'd like
Extract and extend slack/commands/* code for chapters, committees, contribute, projects into slack/common/* files and reuse it for both app home page and commands. Make sure to add a params to control entity summary length (truncation) and other presentation parts that may need to look different. Unify the code and the entities end user's look.

[AbhayTopno]

@arkid15r can you assign thia to me please

[nitinawari]

@arkid15r can i work on this ? I recently implementated to command i have idea about it

[nitinawari]

@arkid15r I’ve completed this task, but there’s an overlap with #427 after extracting the common command code into common/handlers.py.

As discussed with @AbhayTopno in Slack DMs, He handling that task and would like to complete it. Should I avoid extracting the contribution-related code to prevent conflicts?

Also, do you think handlers.py is a good name for the common file, or would you suggest a more descriptive alternative?

[arkid15r]

Yes, let's deal w/ the contribute command later.
Please submit the code and I'll be able to suggest better naming if possible.

Thank you @nitinawari