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/copy.go

@@ -0,0 +1,32 @@
+package storage
+
+import (
+	"net"
+
+	"github.com/qdm12/gluetun/internal/models"
+)
+
+func copyServer(server models.Server) (serverCopy models.Server) {
+	serverCopy = server
+	serverCopy.IPs = copyIPs(server.IPs)
+	return serverCopy
+}
+
+func copyIPs(toCopy []net.IP) (copied []net.IP) {
+	if toCopy == nil {
+		return nil
+	}
+
+	copied = make([]net.IP, len(toCopy))
+	for i := range toCopy {
+		copied[i] = copyIP(toCopy[i])
+	}
+
+	return copied
+}
+
+func copyIP(toCopy net.IP) (copied net.IP) {
+	copied = make(net.IP, len(toCopy))
+	copy(copied, toCopy)
+	return copied
+}