add a new configuration section for HTTP clients

HTTP clients are used for executing hooks such as the ones used for custom
actions, external authentication and pre-login user modifications.

This allows, for example, to use self-signed certificate without defeating the
purpose of using TLS

httpd/httpd_test.go

@@ -105,6 +105,10 @@ func TestMain(m *testing.M) {
 		logger.Warn(logSender, "", "error initializing data provider: %v", err)
 		os.Exit(1)
 	}
+
+	httpConfig := config.GetHTTPConfig()
+	httpConfig.Initialize(configDir)
+
 	dataProvider := dataprovider.GetProvider()
 	httpdConf := config.GetHTTPDConfig()