feat(providers): add AirVPN support (#1145)

internal/provider/utils/openvpn.go

@@ -42,6 +42,7 @@ type OpenVPNProviderSettings struct {
 	RenegDisabled  bool
 	RenegSec       uint16
 	KeyDirection   string
+	SetEnv         map[string]string
 	ExtraLines     []string
 	UDPLines       []string
 	IPv6Lines      []string
@@ -168,6 +169,10 @@ func OpenVPNConfig(provider OpenVPNProviderSettings,
 		lines.addLines(provider.IPv6Lines)
 	}
 
+	for envKey, envValue := range provider.SetEnv {
+		lines.add("setenv", envKey, envValue)
+	}
+
 	if provider.CA != "" {
 		lines.addLines(WrapOpenvpnCA(provider.CA))
 	}