[v2] `/mentor/all/` Route

[harshkhandeparkar]

1. Add a /mentor/all/ (GET, with login) route to fetch a list of all mentors' basic information.
2. Add tests for this route.

[YoganshSharma]

• In v1, it does not return the mentor who makes the request. Do we have to do that here as well?

  KWoC-Backend/controllers/mentor.go

  Line 101 in a0ed591

  err := db.Select([]string{"Name", "Username"}).Not("username", mentor).Find(&mentors).Error

[harshkhandeparkar]

• In v1, it does not return the mentor who makes the request. Do we have to do that here as well?

  KWoC-Backend/controllers/mentor.go

  Line 101 in a0ed591

  err := db.Select([]string{"Name", "Username"}).Not("username", mentor).Find(&mentors).Error

I guess we can return it. The frontend should handle the exclusion imo.