Maint: internal/storage rework

- No more global variables
- Inject merged servers to configuration package
- Fix #566: configuration parsing to use persisted servers.json
- Move server data files from `internal/constants` to `internal/storage`

internal/configuration/vyprvpn.go

@@ -8,13 +8,14 @@ import (
 
 func (settings *Provider) readVyprvpn(r reader) (err error) {
 	settings.Name = constants.Vyprvpn
+	servers := r.servers.GetVyprvpn()
 
 	settings.ServerSelection.TargetIP, err = readTargetIP(r.env)
 	if err != nil {
 		return err
 	}
 
-	settings.ServerSelection.Regions, err = r.env.CSVInside("REGION", constants.VyprvpnRegionChoices())
+	settings.ServerSelection.Regions, err = r.env.CSVInside("REGION", constants.VyprvpnRegionChoices(servers))
 	if err != nil {
 		return fmt.Errorf("environment variable REGION: %w", err)
 	}