Add test scenario for downloading archives and making sure that the user can only download his/her data
Per issue in https://gitlab.com/gitlab-org/gitlab-ce/issues/45689.
This should be automated via Web UI first, then vis the public API, as a second iteration.
**Steps**
* User of a public repository named "user1/download-test" selects "Download as .zip". `/user1/download-test/-/archive/master/download-test-master.zip`
* Before any new changes are made to "user1/download-test", user2 requests "Download zip" from "/user2/download-test". They receive the contents of the `.zip` produced from "/user1/download-test". `/user2/download-test/-/archive/master/download-test-master.zip`
* User2 requests "Download as .tar.gz" of "/user2/download-test". `/user1/download-test/-/archive/master/download-test-master.tar.gz`
**Pseudo code**
- Instantiate `ApiClient1` and log in as `USER1`
- Instantiate `ApiClient2` and log in as `USER2`
- From `ApiClient1` call endpoint to download repo as .zip for `USER1` data
- From `ApiClient2` call endpoint to download repo as .zip for `USER2` data
- Verify that data requested from `USER1` contains only `USER1` data and data requested from `USER2` contains only `USER2` data
issue