PLT-6358: Server HTTP client improvements (#6980)

* restrict untrusted, internal http connections by default

* command test fix

* more test fixes

* change setting from toggle to whitelist

* requested ui changes

* add isdefault diagnostic

* fix tests

api/post_test.go

@@ -188,10 +188,13 @@ func testCreatePostWithOutgoingHook(
 	channel := th.CreateChannel(Client, team)
 
 	enableOutgoingHooks := utils.Cfg.ServiceSettings.EnableOutgoingWebhooks
+	allowedInternalConnections := *utils.Cfg.ServiceSettings.AllowedUntrustedInternalConnections
 	defer func() {
 		utils.Cfg.ServiceSettings.EnableOutgoingWebhooks = enableOutgoingHooks
+		utils.Cfg.ServiceSettings.AllowedUntrustedInternalConnections = &allowedInternalConnections
 	}()
 	utils.Cfg.ServiceSettings.EnableOutgoingWebhooks = true
+	*utils.Cfg.ServiceSettings.AllowedUntrustedInternalConnections = "localhost 127.0.0.1"
 
 	var hook *model.OutgoingWebhook
 	var post *model.Post
@@ -1359,10 +1362,13 @@ func TestGetOpenGraphMetadata(t *testing.T) {
 	Client := th.BasicClient
 
 	enableLinkPreviews := *utils.Cfg.ServiceSettings.EnableLinkPreviews
+	allowedInternalConnections := *utils.Cfg.ServiceSettings.AllowedUntrustedInternalConnections
 	defer func() {
 		*utils.Cfg.ServiceSettings.EnableLinkPreviews = enableLinkPreviews
+		utils.Cfg.ServiceSettings.AllowedUntrustedInternalConnections = &allowedInternalConnections
 	}()
 	*utils.Cfg.ServiceSettings.EnableLinkPreviews = true
+	*utils.Cfg.ServiceSettings.AllowedUntrustedInternalConnections = "localhost 127.0.0.1"
 
 	ogDataCacheMissCount := 0