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()

model/bundle_info_test.go

@@ -0,0 +1,30 @@
+package model
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestBundleInfoForPath(t *testing.T) {
+	dir, err := ioutil.TempDir("", "mm-plugin-test")
+	require.NoError(t, err)
+	defer os.RemoveAll(dir)
+
+	path := filepath.Join(dir, "plugin.json")
+	f, err := os.Create(path)
+	require.NoError(t, err)
+	_, err = f.WriteString(`{"id": "foo"}`)
+	f.Close()
+	require.NoError(t, err)
+
+	info := BundleInfoForPath(dir)
+	assert.Equal(t, info.Path, dir)
+	assert.NotNil(t, info.Manifest)
+	assert.Equal(t, info.ManifestPath, path)
+	assert.Nil(t, info.ManifestError)
+}