Assignee is not set

Hi,

first of all: Great project! I´m currently testing it and spawned a production ready setup with docker-compose -f docker-compose.yml -f docker-compose-prod.yml up and the required environment variables. After that I added a new project by posting to the api endpoint.

The config of this project looks like this:

version: 2
updates:
  - package-ecosystem: nuget
    directory: "/"
    schedule:
        interval: daily
        time: "12:32"
    open-pull-requests-limit: 30
    target-branch: develop
    assignees:
      - M.lueder

Everything ist working fine and the MRs are created but the assignee is not set. I tried it with and without quotes. Am I missing something? We are using a selfhosted GitLab CE 13.11.3