Prevent cookie sharing between same subgroup

What does this MR do?

Prevent cookie sharing between same subgroup

We had already introduced cookie path, which was preventing cookie sharing in browser.
In this MR, we are checking cookie path with request path to prevent cookie sharing programmatically.

Duo has given good explanation here about the implementation.

Related: gitlab#538323

Changelog: added

TODO

• Feature flag
  • Added feature flag:
  • This feature does not require a feature flag
• I added the Changelog trailer to the commits that need to be included in the changelog (e.g. Changelog: added)
• I added unit tests or they are not required
• I added acceptance tests or they are not required
• I added documentation (or it's not required)
• I followed code review guidelines
• I followed Go Style guidelines