Unit test gql helpers

[Ullaakut]

• updateUsers(users []User, response listStargazersResponse, year int) []User
• getCursors(ctx *context.Context, sg []stargazers, totalUsers uint) []string
• buildRequestBody(ctx *context.Context, baseRequest string, pagination int) string
• getCursor(cursors []string, page int, reverseOrder bool) string
• pickRandomStringsExcept(s []string, picked []string, amount uint) []string
• isBlacklisted(user string) bool
• parseResponse(resp *http.Response) (*listStargazersResponse, []byte, error)