Add support for remapping existing labels to new ones

[JacobDB]

This may be too complicated for this script, but I'd love the ability to "translate" my existing labels in to this "sane" format. I only recently started trying to use labels to their fullest extent, so I have 200+ projects in my GitLab instance that have an older format.

Being able to set something in the config file like:

{
    ...,
    "translations": {
        "enhancement": "Type: Enhancement",
        "broken": "Type: Bug",
        "done" : "Status: Completed"
    }
}

I have two thoughts on how this could be achieved:

1. After inserting labels for a project, index all issues. Delete existing labels, and assign translated labels
2. Before inserting labels for a project, index existing labels, and adjust their settings to match the translated value. (i.e. update broken/#FF0000 to Type: Bug/EE0701).

Any thoughts on this? It'd be a great help in getting all my projects reconfigured.

[JacobDB]

Could alternatively set the translations on each new label, like this:

[
    {
        "name": "Type: Bug",
        "color": "#EE0701",
        "priority": 1,
        "board": true,
        "translate": "broken",
    }
]

[JacobDB]

Thinking about it, I think the second option (reconfiguring existing labels) would probably be easiest to implement, but of course I'm not familiar with the API so I could be mistaken.

[JacobDB]

Ah, I should've read the documentation more, I see you do allow deleting existing labels, so this issue is just for remapping existing ones.

[JacobDB]

A year later and I'm thinking about this again :) I'll try and make time to make a pull request...