Plugins: Plugins loader pipeline (#71438)

* discovery

* flesh out

* add docs

* remove unused func

* bootstrap stage

* fix docs

* update docs

* undo unnecessary changes

* add end tag

* update doc

* fix linter

* fix

* tidy

* update docs

* add class to filter func

* apply PR feedback

* fix test

pkg/plugins/manager/pipeline/bootstrap/factory.go

@@ -0,0 +1,76 @@
+package bootstrap
+
+import (
+	"fmt"
+
+	"github.com/grafana/grafana/pkg/plugins"
+	"github.com/grafana/grafana/pkg/plugins/log"
+	"github.com/grafana/grafana/pkg/plugins/manager/loader/assetpath"
+)
+
+type pluginFactoryFunc func(p plugins.FoundPlugin, pluginClass plugins.Class, sig plugins.Signature) (*plugins.Plugin, error)
+
+// DefaultPluginFactory is the default plugin factory used by the Construct step of the Bootstrap stage.
+//
+// It creates the plugin using plugin information found during the Discovery stage and makes use of the assetPath
+// service to set the plugin's BaseURL, Module, Logos and Screenshots fields.
+type DefaultPluginFactory struct {
+	assetPath *assetpath.Service
+}
+
+// NewDefaultPluginFactory returns a new DefaultPluginFactory.
+func NewDefaultPluginFactory(assetPath *assetpath.Service) *DefaultPluginFactory {
+	return &DefaultPluginFactory{assetPath: assetPath}
+}
+
+func (f *DefaultPluginFactory) createPlugin(p plugins.FoundPlugin, class plugins.Class,
+	sig plugins.Signature) (*plugins.Plugin, error) {
+	baseURL, err := f.assetPath.Base(p.JSONData, class, p.FS.Base())
+	if err != nil {
+		return nil, fmt.Errorf("base url: %w", err)
+	}
+	moduleURL, err := f.assetPath.Module(p.JSONData, class, p.FS.Base())
+	if err != nil {
+		return nil, fmt.Errorf("module url: %w", err)
+	}
+
+	plugin := &plugins.Plugin{
+		JSONData:      p.JSONData,
+		FS:            p.FS,
+		BaseURL:       baseURL,
+		Module:        moduleURL,
+		Class:         class,
+		Signature:     sig.Status,
+		SignatureType: sig.Type,
+		SignatureOrg:  sig.SigningOrg,
+	}
+	plugin.SetLogger(log.New(fmt.Sprintf("plugin.%s", plugin.ID)))
+
+	if err = setImages(plugin, f.assetPath); err != nil {
+		return nil, err
+	}
+
+	return plugin, nil
+}
+
+func setImages(p *plugins.Plugin, assetPath *assetpath.Service) error {
+	var err error
+	for _, dst := range []*string{&p.Info.Logos.Small, &p.Info.Logos.Large} {
+		*dst, err = assetPath.RelativeURL(p, *dst, defaultLogoPath(p.Type))
+		if err != nil {
+			return fmt.Errorf("logo: %w", err)
+		}
+	}
+	for i := 0; i < len(p.Info.Screenshots); i++ {
+		screenshot := &p.Info.Screenshots[i]
+		screenshot.Path, err = assetPath.RelativeURL(p, screenshot.Path, "")
+		if err != nil {
+			return fmt.Errorf("screenshot %d relative url: %w", i, err)
+		}
+	}
+	return nil
+}
+
+func defaultLogoPath(pluginType plugins.Type) string {
+	return fmt.Sprintf("public/img/icn-%s.svg", string(pluginType))
+}