Refactor (#174)

- Goal was to simplify main.go complexity
- Use common structures and interfaces for all vpn providers
- Moved files around
- Removed some alias models

internal/models/servers.go

@@ -0,0 +1,33 @@
+package models
+
+import "net"
+
+type PIAServer struct {
+	IPs    []net.IP
+	Region string
+}
+
+type MullvadServer struct {
+	IPs         []net.IP
+	Country     string
+	City        string
+	ISP         string
+	Owned       bool
+	DefaultPort uint16
+}
+
+type WindscribeServer struct {
+	Region string
+	IPs    []net.IP
+}
+
+type SurfsharkServer struct {
+	Region string
+	IPs    []net.IP
+}
+
+type CyberghostServer struct {
+	Region string
+	Group  string
+	IPs    []net.IP
+}