Implement experimental REST API endpoints for plugins (#7279)

* Implement experimental REST API endpoints for plugins

* Updates per feedback and rebase

* Update tests

* Further updates

* Update extraction of plugins

* Use OS temp dir for plugins instead of search path

* Fail extraction on paths that attempt to traverse upward

* Update pluginenv ActivePlugins()

plugin/pluginenv/search_path.go

@@ -4,7 +4,7 @@ import (
 	"io/ioutil"
 	"path/filepath"
 
-	"github.com/mattermost/platform/plugin"
+	"github.com/mattermost/platform/model"
 )
 
 // Performs a full scan of the given path.
@@ -14,17 +14,17 @@ import (
 // parsed).
 //
 // Plugins are found non-recursively and paths beginning with a dot are always ignored.
-func ScanSearchPath(path string) ([]*plugin.BundleInfo, error) {
+func ScanSearchPath(path string) ([]*model.BundleInfo, error) {
 	files, err := ioutil.ReadDir(path)
 	if err != nil {
 		return nil, err
 	}
-	var ret []*plugin.BundleInfo
+	var ret []*model.BundleInfo
 	for _, file := range files {
 		if !file.IsDir() || file.Name()[0] == '.' {
 			continue
 		}
-		if info := plugin.BundleInfoForPath(filepath.Join(path, file.Name())); info.ManifestPath != "" {
+		if info := model.BundleInfoForPath(filepath.Join(path, file.Name())); info.ManifestPath != "" {
 			ret = append(ret, info)
 		}
 	}