Provisioning: Add API endpoint to reload provisioning configs (#16579)

* Add api to reaload provisioning

* Refactor and simplify the polling code

* Add test for the provisioning service

* Fix provider initialization and move some code to file reader

* Simplify the code and move initialization

* Remove unused code

* Update comment

* Add comment

* Change error messages

* Add DashboardProvisionerFactory type

* Update imports

* Use new assert lib

* Use mutext for synchronizing the reloading

* Fix typo

Co-Authored-By: aocenas <mr.ocenas@gmail.com>

* Add docs about the new api

pkg/api/admin_provisioning.go

@@ -0,0 +1,30 @@
+package api
+
+import (
+	"context"
+	"github.com/grafana/grafana/pkg/models"
+)
+
+func (server *HTTPServer) AdminProvisioningReloadDasboards(c *models.ReqContext) Response {
+	err := server.ProvisioningService.ProvisionDashboards()
+	if err != nil && err != context.Canceled {
+		return Error(500, "", err)
+	}
+	return Success("Dashboards config reloaded")
+}
+
+func (server *HTTPServer) AdminProvisioningReloadDatasources(c *models.ReqContext) Response {
+	err := server.ProvisioningService.ProvisionDatasources()
+	if err != nil {
+		return Error(500, "", err)
+	}
+	return Success("Datasources config reloaded")
+}
+
+func (server *HTTPServer) AdminProvisioningReloadNotifications(c *models.ReqContext) Response {
+	err := server.ProvisioningService.ProvisionNotifications()
+	if err != nil {
+		return Error(500, "", err)
+	}
+	return Success("Notifications config reloaded")
+}