admin: adds paging to global user list

Currently there is a limit of 1000 users in the global
user list. This change introduces paging so that an
admin can see all users and not just the first 1000.

Adds a new route to the api - /api/users/search that
returns a list of users and a total count. It takes
two parameters perpage and page that enable paging.

Fixes #7469

pkg/services/sqlstore/user_test.go

@@ -0,0 +1,45 @@
+package sqlstore
+
+import (
+	"fmt"
+	"testing"
+
+	. "github.com/smartystreets/goconvey/convey"
+
+	"github.com/grafana/grafana/pkg/models"
+)
+
+func TestUserDataAccess(t *testing.T) {
+
+	Convey("Testing DB", t, func() {
+		InitTestDB(t)
+
+		var err error
+		for i := 0; i < 5; i++ {
+			err = CreateUser(&models.CreateUserCommand{
+				Email: fmt.Sprint("user", i, "@test.com"),
+				Name:  fmt.Sprint("user", i),
+				Login: fmt.Sprint("user", i),
+			})
+			So(err, ShouldBeNil)
+		}
+
+		Convey("Can return the first page of users and a total count", func() {
+			query := models.SearchUsersQuery{Query: "", Page: 1, Limit: 3}
+			err = SearchUsers(&query)
+
+			So(err, ShouldBeNil)
+			So(len(query.Result.Users), ShouldEqual, 3)
+			So(query.Result.TotalCount, ShouldEqual, 5)
+		})
+
+		Convey("Can return the second page of users and a total count", func() {
+			query := models.SearchUsersQuery{Query: "", Page: 2, Limit: 3}
+			err = SearchUsers(&query)
+
+			So(err, ShouldBeNil)
+			So(len(query.Result.Users), ShouldEqual, 2)
+			So(query.Result.TotalCount, ShouldEqual, 5)
+		})
+	})
+}