refactor(storage): new storage file structure

- new directory structure containing manifest.json and one json file per provider, by default.
- the manifest.json file can specify a filepath for each vpn provider
- each vpn provider json data file can contain the `"preferred": true` field to enforce it is used even if outdated, unless there is a version mismatch
- `STORAGE_SERVERS_DIRECTORY_PATH` replaces `STORAGE_FILEPATH` (which is now a migration source only). It sets the directory where server manifest and per-provider JSON files are stored (default: `/gluetun/servers/`).
- First-run migration: On startup, gluetun checks for the old /gluetun/servers.json file; if found and no new manifest exists, it automatically migrates all data to /gluetun/servers/ directory structure
- Silent fallback: If legacy file isn't found, uses the new directory path normally
- Legacy cleanup: After successful migration, attempts to remove the old fat JSON file (logs warning only if removal fails, e.g., read-only bind mounts)

gluetun-servers/pkg/publicip/api/resilient_test.go

@@ -0,0 +1,70 @@
+package api
+
+import (
+	"testing"
+
+	"github.com/qdm12/gluetun-servers/pkg/publicip/models"
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_GetMostPopularResult(t *testing.T) {
+	t.Parallel()
+
+	testCases := map[string]struct {
+		input    []models.PublicIP
+		expected models.PublicIP
+	}{
+		"exact_matches": {
+			input: []models.PublicIP{
+				{Country: "France", City: "Paris"},
+				{Country: "USA", City: "New York"},
+				{Country: "France", City: "Paris"},
+			},
+			expected: models.PublicIP{Country: "France", City: "Paris"},
+		},
+		"fuzzy_country_matching": {
+			input: []models.PublicIP{
+				{Country: "Germany", Region: "Bavaria", City: "Munich"},
+				{Country: "Germani", Region: "Bavaria", City: "Munich"},
+				{Country: "France", Region: "IDF", City: "Paris"},
+			},
+			expected: models.PublicIP{Country: "Germany", Region: "Bavaria", City: "Munich"},
+		},
+		"hierarchy_priority": {
+			input: []models.PublicIP{
+				{Country: "Italy", Region: "Sicily", City: "Syracuse"},
+				{Country: "Italy", Region: "Sicily", City: "Syracuse"},
+				{Country: "USA", Region: "New York", City: "Syracuse"},
+				{Country: "Italy", Region: "Sicily", City: "Syracuse"},
+			},
+			expected: models.PublicIP{Country: "Italy", Region: "Sicily", City: "Syracuse"},
+		},
+		"normalization_check": {
+			input: []models.PublicIP{
+				{Country: "Canada", City: "Montréal"},
+				{Country: "Canada", City: "Montreal "},
+				{Country: "UK", City: "London"},
+			},
+			expected: models.PublicIP{Country: "Canada", City: "Montréal"},
+		},
+		"all_different": {
+			input: []models.PublicIP{
+				{Country: "Canada", City: "Montréal"},
+				{Country: "US", City: "New York"},
+				{Country: "UK", City: "London"},
+			},
+			expected: models.PublicIP{Country: "US", City: "New York"},
+		},
+	}
+
+	for name, testCase := range testCases {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+			result := getMostPopularResult(testCase.input)
+
+			assert.Equal(t, testCase.expected.Country, result.Country)
+			assert.Equal(t, testCase.expected.Region, result.Region)
+			assert.Equal(t, testCase.expected.City, result.City)
+		})
+	}
+}