How to associate custom attributes via API?

I’ve created a Slack integration for my coworkers that allows them to create Taiga issues via a Slack command, opening a creation assistant through a few modals. All important fields are present, including custom attributes we use.

I managed to create the issue at the end of the workflow, but I’m unsure how to associate custom attributes with issues or even stories.

Can someone enlighten me?

Solution found !

I’ve analyzed the requests send on my behalf when using the app and found the corresponding endpoint.

So for others who need a solution there is some endpoints missing in the API docs.

PATCH /api/v1/webhooks/issues/custom-attributes-values/<id>
    "attributes_values": {
          <attribute_id>: "<text_value>"
    "version": <version>