chore(all): memory and thread safe storage

- settings: get filter choices from storage for settings validation
- updater: update servers to the storage
- storage: minimal deep copying and data duplication
- storage: add merged servers mutex for thread safety
- connection: filter servers in storage
- formatter: format servers to Markdown in storage
- PIA: get server by name from storage directly
- Updater: get servers count from storage directly
- Updater: equality check done in storage, fix #882

internal/storage/choices.go

@@ -0,0 +1,27 @@
+package storage
+
+import (
+	"github.com/qdm12/gluetun/internal/configuration/settings/validation"
+	"github.com/qdm12/gluetun/internal/constants/providers"
+	"github.com/qdm12/gluetun/internal/models"
+)
+
+func (s *Storage) GetFilterChoices(provider string) models.FilterChoices {
+	if provider == providers.Custom {
+		return models.FilterChoices{}
+	}
+
+	s.mergedMutex.RLock()
+	defer s.mergedMutex.RUnlock()
+
+	serversObject := s.getMergedServersObject(provider)
+	servers := serversObject.Servers
+	return models.FilterChoices{
+		Countries: validation.ExtractCountries(servers),
+		Regions:   validation.ExtractRegions(servers),
+		Cities:    validation.ExtractCities(servers),
+		ISPs:      validation.ExtractISPs(servers),
+		Names:     validation.ExtractServerNames(servers),
+		Hostnames: validation.ExtractHostnames(servers),
+	}
+}