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/provider/privateinternetaccess/provider.go

@@ -5,11 +5,11 @@ import (
 	"time"
 
 	"github.com/qdm12/gluetun/internal/constants/openvpn"
-	"github.com/qdm12/gluetun/internal/models"
+	"github.com/qdm12/gluetun/internal/provider/common"
 )
 
 type Provider struct {
-	servers    []models.Server
+	storage    common.Storage
 	randSource rand.Source
 	timeNow    func() time.Time
 	// Port forwarding
@@ -17,11 +17,11 @@ type Provider struct {
 	authFilePath    string
 }
 
-func New(servers []models.Server, randSource rand.Source,
+func New(storage common.Storage, randSource rand.Source,
 	timeNow func() time.Time) *Provider {
 	const jsonPortForwardPath = "/gluetun/piaportforward.json"
 	return &Provider{
-		servers:         servers,
+		storage:         storage,
 		timeNow:         timeNow,
 		randSource:      randSource,
 		portForwardPath: jsonPortForwardPath,