fabric-eraser-migration-v1-v2.js

function migrateObject(obj) {
    const clipPath = obj?.clipPath;
    if (clipPath && clipPath.type === 'group' && clipPath.eraser === true) {
        clipPath.type = 'eraser';
        delete clipPath.eraser;
        const rect = clipPath.objects.shift();
        obj.clipPath = rect.clipPath;
        obj.eraser = clipPath;
    }
}

function traverseTree(target) {
    target.objects?.forEach(obj => {
        migrateObject(obj);
        migrateObject(obj.clipPath);
        traverseTree(obj);
    });
}

/**
 * call this method
 * @param {Object} canvasJSON 
 * @returns {Object} version 2 compatible json
 */
function migrate(canvasJSON) {
    traverseTree(canvasJSON);
    ['backgroundImage', 'overlayImage'].forEach(key => {
        if (canvasJSON[key]) {
            migrateObject(canvasJSON[key]);
            traverseTree(canvasJSON[key]);
        }
    });
    return canvasJSON;
}

Call migrate with the json payload.
It returns a migrated payload.
It's safe to run on v2 payload if you're not sure if your payload is up to date or not.