Fix errors on openapi client generation

This MR improves the openapi specs so that we can generate a client by running:

#!/bin/bash

function get_openapi {
    url="https://localhost/backend/api/v1/openapi.json"
    out="openapi.json"
    curl --insecure $url --output $out
    format_json $out
}

function generate_client {
    docker run --rm -v $PWD:/local openapitools/openapi-generator-cli generate -i /local/openapi.json -g python -o /local/out/python
}

function main {
    if [ "$1" == "openapi.json" ]; then
        get_openapi
    elif [ "$1" == "client" ]; then
        generate_client
    else
        echo "Unknown target $1"
    fi
}

main "$@"

with ./manage.sh openapi.json && ./manage.sh client.