add an UI element to indicate taken/free issues

[zugdev]

A big advantage of scouting issues on GitHub instead of the directory is that we can't differentiate between taken and open issues. GitHub solves that by displaying the assignee's PFP:

We should add a UI element to differentiate between issues with an assignee and issues without one, also allowing to filter by the presence or absence of assignee. This should be very easy to do given that the issue object has the following structure:

{
       "assignee": {
        "login": "imabutahersiddik",
        "id": 138387257,
        "node_id": "U_kgDOCD-fOQ",
        "avatar_url": "https://avatars.githubusercontent.com/u/138387257?v=4",
        "gravatar_id": "",
        "url": "https://api.github.com/users/imabutahersiddik",
        "html_url": "https://github.com/imabutahersiddik",
        "followers_url": "https://api.github.com/users/imabutahersiddik/followers",
        "following_url": "https://api.github.com/users/imabutahersiddik/following{/other_user}",
        "gists_url": "https://api.github.com/users/imabutahersiddik/gists{/gist_id}",
        "starred_url": "https://api.github.com/users/imabutahersiddik/starred{/owner}{/repo}",
        "subscriptions_url": "https://api.github.com/users/imabutahersiddik/subscriptions",
        "organizations_url": "https://api.github.com/users/imabutahersiddik/orgs",
        "repos_url": "https://api.github.com/users/imabutahersiddik/repos",
        "events_url": "https://api.github.com/users/imabutahersiddik/events{/privacy}",
        "received_events_url": "https://api.github.com/users/imabutahersiddik/received_events",
        "type": "User",
        "user_view_type": "public",
        "site_admin": false
    },
    "url": "https://api.github.com/repos/ubiquity-os-marketplace/text-conversation-rewards/issues/152",
    "repository_url": "https://api.github.com/repos/ubiquity-os-marketplace/text-conversation-rewards",
    "title": "Failed to save permit",
   ...
}

An instance as example:

[0x4007]

The task is not supposed to be visible if it's taken. Perhaps this feature is broken now? Maybe this approach does make sense for the ability to see every task in the network, but then to be able to further sort for availability.

These days I even use the UI to quickly find some issue I was thinking about (it's way faster than any official GitHub UI for this purpose) so it could be nice to see regardless of its assigned status.

[zugdev]

It's broken, but yes, I imagine the DevPool as an important tooling not only for contributors finding an issue to tackle, but also for code owners to manage/view it all. Therefore I believe this is a nice feature to have. We should find the old broken code and remove it too.

[0x4007]

It's related to the unavailable label on the backend. When assigned it would add that label. I suppose the UI would then filter out those with the unavailable label.