App Plugins: Add backend support (#28272)

* Add backend support for app plugins

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>
Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

pkg/plugins/app_plugin.go

@@ -2,12 +2,15 @@ package plugins
 
 import (
 	"encoding/json"
+	"path/filepath"
 	"strings"
 
 	"github.com/gosimple/slug"
 	"github.com/grafana/grafana/pkg/models"
 	"github.com/grafana/grafana/pkg/plugins/backendplugin"
+	"github.com/grafana/grafana/pkg/plugins/backendplugin/grpcplugin"
 	"github.com/grafana/grafana/pkg/setting"
+	"github.com/grafana/grafana/pkg/util/errutil"
 )
 
 type AppPluginCss struct {
@@ -21,6 +24,8 @@ type AppPlugin struct {
 
 	FoundChildPlugins []*PluginInclude `json:"-"`
 	Pinned            bool             `json:"-"`
+
+	Executable string `json:"executable,omitempty"`
 }
 
 // AppPluginRoute describes a plugin route that is defined in
@@ -67,6 +72,15 @@ func (app *AppPlugin) Load(decoder *json.Decoder, base *PluginBase, backendPlugi
 		return err
 	}
 
+	if app.Backend {
+		cmd := ComposePluginStartCommand(app.Executable)
+		fullpath := filepath.Join(app.PluginDir, cmd)
+		factory := grpcplugin.NewBackendPlugin(app.Id, fullpath, grpcplugin.PluginStartFuncs{})
+		if err := backendPluginManager.Register(app.Id, factory); err != nil {
+			return errutil.Wrapf(err, "failed to register backend plugin")
+		}
+	}
+
 	Apps[app.Id] = app
 	return nil
 }