2.x to 3.x

If you're using MongoDB as configuration database run the following script against api_specs collection:

db.getCollection('api_specs').find({}).forEach(function(doc) {
    doc.plugins = [];

    var corsMeta = doc.cors_meta || {enabled: false};
    doc.plugins.push({
        "name": "cors",
        "enabled": !!corsMeta.enabled,
        "config": corsMeta
    });
    delete doc.plugins[0].config.enabled;

    var rateLimit = doc.rate_limit || {enabled: false, limit: 0};
    doc.plugins.push({
        "name": "rate_limit",
        "enabled": !!rateLimit.enabled,
        "config": {
            "limit": rateLimit.limit,
            "policy": "local"
        }
    });

    doc.plugins.push({
        "name": "oauth2",
        "enabled": !!doc.use_oauth2,
        "config": {"server_name": doc.oauth_server_name || null}
    });

    doc.plugins.push({
        "name": "compression",
        "enabled": !!doc.use_compression
    });

    delete doc.rate_limit;
    delete doc.cors_meta;
    delete doc.use_oauth2;
    delete doc.use_basic_auth;
    delete doc.use_compression;

    doc.updated_at = new Date();
    db.api_specs.update({"_id": doc._id}, doc);
});