Feature: LDAP refactoring (#16950)

* incapsulates multipleldap logic under one module

* abstracts users upsert and get logic

* changes some of the text error messages and import sort sequence

* heavily refactors the LDAP module – LDAP module now only deals with LDAP related behaviour

* integrates affected auth_proxy module and their tests

* refactoring of the auth_proxy logic

pkg/services/user/user.go

@@ -0,0 +1,39 @@
+package user
+
+import (
+	"github.com/grafana/grafana/pkg/bus"
+	"github.com/grafana/grafana/pkg/models"
+)
+
+// UpsertArgs are object for Upsert method
+type UpsertArgs struct {
+	ReqContext    *models.ReqContext
+	ExternalUser  *models.ExternalUserInfo
+	SignupAllowed bool
+}
+
+// Upsert add/update grafana user
+func Upsert(args *UpsertArgs) (*models.User, error) {
+	query := &models.UpsertUserCommand{
+		ReqContext:    args.ReqContext,
+		ExternalUser:  args.ExternalUser,
+		SignupAllowed: args.SignupAllowed,
+	}
+	err := bus.Dispatch(query)
+	if err != nil {
+		return nil, err
+	}
+
+	return query.Result, nil
+}
+
+// Get the users
+func Get(
+	query *models.SearchUsersQuery,
+) ([]*models.UserSearchHitDTO, error) {
+	if err := bus.Dispatch(query); err != nil {
+		return nil, err
+	}
+
+	return query.Result.Users, nil
+}