feat(gcp): add GCP plugin (#5229)

Add GCP as a supported plugin for dynamic host catalogs

internal/daemon/controller/controller.go

@@ -320,6 +320,8 @@ func New(ctx context.Context, conf *Config) (*Controller, error) {
 			if _, err := conf.RegisterPlugin(ctx, pluginType, client, []plugin.PluginType{plugin.PluginTypeHost}, plugin.WithDescription(fmt.Sprintf("Built-in %s host plugin", enabledPlugin.String()))); err != nil {
 				return nil, fmt.Errorf("error registering %s host plugin: %w", pluginType, err)
 			}
+		case enabledPlugin == base.EnabledPluginGCP && !c.conf.SkipPlugins:
+			fallthrough
 		case enabledPlugin == base.EnabledPluginAws && !c.conf.SkipPlugins:
 			pluginType := strings.ToLower(enabledPlugin.String())
 			client, cleanup, err := external_plugins.CreateHostPlugin(

internal/daemon/controller/controller_test.go

@@ -257,6 +257,7 @@ func TestController_NewPluginsConfig(t *testing.T) {
 	conf.EnabledPlugins = []base.EnabledPlugin{
 		base.EnabledPluginAws,
 		base.EnabledPluginHostAzure,
+		base.EnabledPluginGCP,
 	}
 
 	_, err = New(testCtx, conf)
@@ -265,14 +266,15 @@ func TestController_NewPluginsConfig(t *testing.T) {
 	// Check that both plugins were written to the temp dir
 	files, err := os.ReadDir(tmpDir)
 	require.NoError(err)
-	require.Len(files, 2)
+	require.Len(files, 3)
 	for _, file := range files {
 		name := filepath.Base(file.Name())
 		// Remove random chars and hyphen
 		name = name[0 : len(name)-6]
 		switch name {
 		case boundary_plugin_assets.PluginPrefix + "aws",
-			boundary_plugin_assets.PluginPrefix + "azure":
+			boundary_plugin_assets.PluginPrefix + "azure",
+			boundary_plugin_assets.PluginPrefix + "gcp":
 		default:
 			require.Fail("unexpected name", name)
 		}