Plugins: Refactor plugin dashboards (#44315)

Moves/refactor Grafana specific functionality related to plugin dashboards 
out to specific services for importing dashboards and keep app plugin dashboards
up-to-date.

Fixes #44257

pkg/api/apierrors/dashboard.go

@@ -0,0 +1,49 @@
+package apierrors
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+
+	"github.com/grafana/grafana/pkg/api/response"
+	"github.com/grafana/grafana/pkg/models"
+	"github.com/grafana/grafana/pkg/plugins"
+	"github.com/grafana/grafana/pkg/services/alerting"
+	"github.com/grafana/grafana/pkg/util"
+)
+
+// ToDashboardErrorResponse returns a different response status according to the dashboard error type
+func ToDashboardErrorResponse(ctx context.Context, pluginStore plugins.Store, err error) response.Response {
+	var dashboardErr models.DashboardErr
+	if ok := errors.As(err, &dashboardErr); ok {
+		if body := dashboardErr.Body(); body != nil {
+			return response.JSON(dashboardErr.StatusCode, body)
+		}
+		if dashboardErr.StatusCode != http.StatusBadRequest {
+			return response.Error(dashboardErr.StatusCode, dashboardErr.Error(), err)
+		}
+		return response.Error(dashboardErr.StatusCode, dashboardErr.Error(), nil)
+	}
+
+	if errors.Is(err, models.ErrFolderNotFound) {
+		return response.Error(http.StatusBadRequest, err.Error(), nil)
+	}
+
+	var validationErr alerting.ValidationError
+	if ok := errors.As(err, &validationErr); ok {
+		return response.Error(http.StatusUnprocessableEntity, validationErr.Error(), err)
+	}
+
+	var pluginErr models.UpdatePluginDashboardError
+	if ok := errors.As(err, &pluginErr); ok {
+		message := fmt.Sprintf("The dashboard belongs to plugin %s.", pluginErr.PluginId)
+		// look up plugin name
+		if plugin, exists := pluginStore.Plugin(ctx, pluginErr.PluginId); exists {
+			message = fmt.Sprintf("The dashboard belongs to plugin %s.", plugin.Name)
+		}
+		return response.JSON(http.StatusPreconditionFailed, util.DynMap{"status": "plugin-dashboard", "message": message})
+	}
+
+	return response.Error(http.StatusInternalServerError, "Failed to save dashboard", err)
+}