Auth: Add anonymous authn client (#59637)

* Authn: Add Client interface and Reqeust and Identity structures

* Authn: Implement Authenticate method in service

* Authn: Add tracing

* Authn: Add logger

* AuthN: Implement Anonymous client

pkg/services/authn/authn.go

@@ -1,4 +1,45 @@
 package authn
 
+import (
+	"context"
+	"net/http"
+
+	"github.com/grafana/grafana/pkg/services/org"
+	"github.com/grafana/grafana/pkg/services/user"
+)
+
+const (
+	ClientAnonymous = "auth.anonymous"
+)
+
 type Service interface {
+	Authenticate(ctx context.Context, client string, r *Request) (*Identity, error)
+}
+
+type Client interface {
+	Authenticate(ctx context.Context, r *Request) (*Identity, error)
+}
+
+type Request struct {
+	HTTPRequest *http.Request
+}
+
+type Identity struct {
+	OrgID       int64
+	OrgName     string
+	IsAnonymous bool
+	OrgRoles    map[int64]org.RoleType
+}
+
+func (i *Identity) Role() org.RoleType {
+	return i.OrgRoles[i.OrgID]
+}
+
+func (i *Identity) SignedInUser() *user.SignedInUser {
+	return &user.SignedInUser{
+		OrgID:       i.OrgID,
+		OrgName:     i.OrgName,
+		OrgRole:     i.Role(),
+		IsAnonymous: i.IsAnonymous,
+	}
 }