Replace signed in user for identity.requester (#73750)

* Make identity.Requester available at Context

* Clean pkg/services/guardian/guardian.go

* Clean guardian provider and guardian AC

* Clean pkg/api/team.go

* Clean ctxhandler, datasources, plugin and live

* Question: what to do with the UserDisplayDTO?

* Clean dashboards and guardian

* Remove identity.Requester from ReqContext

* Implement NewUserDisplayDTOFromRequester

* Fix tests

* Change status code numbers for http constants

* Upgrade signature of ngalert services

* log parsing errors instead of throwing error

* Fix tests and add logs

* linting

pkg/services/dashboards/models.go

@@ -9,6 +9,7 @@ import (
 	"github.com/grafana/grafana/pkg/kinds"
 	"github.com/grafana/grafana/pkg/kinds/dashboard"
 	"github.com/grafana/grafana/pkg/models"
+	"github.com/grafana/grafana/pkg/services/auth/identity"
 	"github.com/grafana/grafana/pkg/services/folder"
 	"github.com/grafana/grafana/pkg/services/org"
 	"github.com/grafana/grafana/pkg/services/quota"
@@ -337,7 +338,7 @@ type GetDashboardRefByIDQuery struct {
 type SaveDashboardDTO struct {
 	OrgID     int64
 	UpdatedAt time.Time
-	User      *user.SignedInUser
+	User      identity.Requester
 	Message   string
 	Overwrite bool
 	Dashboard *Dashboard