Add Slackbot notification when project has been claimed by copilot

[fnisen]

Would be good to let copilots know when a project is no longer available, so they don't need to click through unnecessarily

[parthshah]

Post a message only when a copilot is added in 'is_review' or 'active' project status and total copilot count is < 2.
@fnisen - we should restrict it to these 2 states to ensure a message is posted only if the project was available to be claimed at some time.
Note: Please provide the text for the slack notification

[fnisen]

@parthshah that's good thinking, but shouldn't it actually be when a copilot is added in "reviewed" phase? That's the phase that makes a project claimable for copilots.

• For the copy, can we actually show the handle of the copilot in the message? So, copy would be:
  "(Copilot handle) has claimed a project. Welcome to the team!" And then the rest of the attributes: Title, Description, Project type, post time

• Option 2 would be putting the copilot name in the Slack post body. Let me know if that's the only way to do it or is much easier of an implementation

• Also, can we change the avatars, like so, to make the difference more obvious:
  --- Original post:

--- Follow up post that project has been claimed:

Please see more details on the avatars here: #65 (comment)

[parthshah]

➤ Parth commented:
I would like to include active state as well, in case a project manager goes moves it to active state without adding a copilot.
Yes we can use those avatars -- @uttpal please see above