Feat: multiple OpenVPN ciphers for negotiation

- Perfect privacy to accept AES-256-CBC and AES-256-GCM
- Cyberghost default cipher set to AES-256-GCM
- `OPENVPN_CIPHER` accept comma separated cipher values
- Use `ncp-ciphers` for OpenVPN 2.4

internal/provider/utils/cipher_test.go

@@ -9,24 +9,31 @@ import (
 func Test_CipherLines(t *testing.T) {
 	t.Parallel()
 	testCases := map[string]struct {
+		ciphers []string
 		version string
 		lines   []string
 	}{
 		"empty version": {
+			ciphers: []string{"AES"},
 			lines: []string{
 				"data-ciphers-fallback AES",
 				"data-ciphers AES",
 			},
 		},
 		"2.4": {
+			ciphers: []string{"AES", "CBC"},
 			version: "2.4",
-			lines:   []string{"cipher AES"},
+			lines: []string{
+				"cipher AES",
+				"ncp-ciphers AES:CBC",
+			},
 		},
 		"2.5": {
+			ciphers: []string{"AES", "CBC"},
 			version: "2.5",
 			lines: []string{
 				"data-ciphers-fallback AES",
-				"data-ciphers AES",
+				"data-ciphers AES:CBC",
 			},
 		},
 	}
@@ -35,9 +42,7 @@ func Test_CipherLines(t *testing.T) {
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
 
-			const cipher = "AES"
-
-			lines := CipherLines(cipher, testCase.version)
+			lines := CipherLines(testCase.ciphers, testCase.version)
 
 			assert.Equal(t, testCase.lines, lines)
 		})