Manage labels across repos and orgs

[bastelfreak]

We need to ensure that certain labels are present in a repository and also configured in the whole org: https://github.com/organizations/voxpupuli/settings/labels

[bastelfreak]

A little bit of insights:

• We need to sync all labels from all repos
• We need to update labels if their colour and/or description does not match
• We need to add labels that aren't configured at all in a repository

This is implemented in #135

ToDo:

• To the same for the whole organisation (https://github.com/organizations/voxpupuli/settings/labels)
• Fix labels that are marked as an alias in our yaml and exist in a repo
• Display labels, that exist in an repository but not in our yaml, in our frontend.

In those cases a collaborator needs to:

• Check if the label is used at any issue or pull-request
• Decide if we need to drop the label from the repo, or
• if it should be added to our yaml as new label, or
• if it should be added as an alias to an existing label in our config

[Flipez]

How do we want to migrate alias labels?

One idea would be to rename the alias to 'alias (deprecated)' and attach the original label to the PR or issue.

Another one would be to completely remove the alias and only attach the new one.