[GFI] Add automatic project management for Assigned tasks

[p-wysocki]

Details:

• Up until now tasks on GFI board have to be manually moved between "Contributors needed" and "Assigned" columns
• This action automates that task
• When a user is assigned to the task, it gets moved to "Assigned" column
• When a user is unassigned from the task, it gets moved to "Contributors needed" column
• Tested and working properly in my fork, in a copy of GFI Project
• May need some tweaking for master (it needs merge for testing)
• Requires a Personal Access Token with broader permissions than secrets.GITHUB_TOKEN (I added it as secrets.GFI_PAT, perhaps there's a better way?)

Tickets:

• N/A

[p-wysocki]

@ilya-lavrenov @akladiev could you please take a look?

One caveat is that secrets.GITHUB_TOKEN has insufficient permissions for modifying and reading projects/issues, we need a new token (which I called secrets.GFI_PAT) or perhaps an extension of secrets.GITHUB_TOKEN permissions.

[mlukasze]

@akladiev please, take a look
thanks in advance!

[mlukasze]

@akladiev any objections, or could we merge it? :)