feat: add an example of a join query with a group by but using confidential go app.

[qascade]

feat: add an example of a join query with a group by but using confidential go app.

[Sarthak027]

Hey,
I want to work on this issue. Can you assign me on this issue under Gssoc'23.

[qascade]

@Sarthak027 Awesome. Assigning this to you. You will have to understand Google's differential privacy definition and how it works. Please note, SQL is just for understanding you will have to write a go template that compiles and does same thing as what SQL query will do. Let me know if you have any further questions. Name the branch feat.join_goapp

Google Repo: https://github.com/google/differential-privacy
Video: https://youtu.be/1F6pRMVGWdc
Paper: https://arxiv.org/abs/1909.01917