Aggregation how to merge content from two schemas

Working with Data Node.js Frameworks
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1

i want to retrieve all posts

const blogs = await Blog.aggregate([
            {
                $lookup: {
                    from: "tags",
                    localField: "author",
                    foreignField: "_id",
                    as: "blog_tags"
                }
            },
        ])

this code displays the posts like this

image
image894×994 111 KB

but i want to merge what is in blog_tags and make it in parent blog(bring it to the front)
blog model:

const BlogSchema = new mongoose.Schema(
    {
        
        title: {
            type: String
          },
          content: {
            type: String
          },
          author: {
            type: mongoose.Schema.Types.ObjectId,
            ref: Tags
          },
          content_type: {
            type: mongoose.Schema.Types.ObjectId,
            ref: Tags
          },
}

tag schema:

const TagSchema = new Schema({
    name: {
        type: String
    },
    type: {
        type: Object,
    },
    color: {
        type: String
    },
    timestamp: {
        type: Date,
        default: Date.now
    },
});