platform: modularize api/gui, add docs-tests-web foundation, and refresh root config

selective-vpn-api/app/dns_settings_state_upstreams_pool_store.go

@@ -0,0 +1,53 @@
+package app
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+)
+
+func saveDNSUpstreamPoolFile(items []DNSUpstreamPoolItem) error {
+	state := DNSUpstreamPoolState{Items: normalizeDNSUpstreamPoolItems(items)}
+	if err := os.MkdirAll(filepath.Dir(dnsUpstreamPool), 0o755); err != nil {
+		return err
+	}
+	tmp := dnsUpstreamPool + ".tmp"
+	b, err := json.MarshalIndent(state, "", "  ")
+	if err != nil {
+		return err
+	}
+	if err := os.WriteFile(tmp, b, 0o644); err != nil {
+		return err
+	}
+	return os.Rename(tmp, dnsUpstreamPool)
+}
+
+func loadDNSUpstreamPoolState() []DNSUpstreamPoolItem {
+	data, err := os.ReadFile(dnsUpstreamPool)
+	if err == nil {
+		var st DNSUpstreamPoolState
+		if json.Unmarshal(data, &st) == nil {
+			items := normalizeDNSUpstreamPoolItems(st.Items)
+			if len(items) > 0 {
+				return items
+			}
+		}
+	}
+	legacy := loadDNSUpstreamsConfFile()
+	items := dnsUpstreamPoolFromLegacy(legacy)
+	if len(items) > 0 {
+		_ = saveDNSUpstreamPoolFile(items)
+	}
+	return items
+}
+
+func saveDNSUpstreamPoolState(items []DNSUpstreamPoolItem) error {
+	items = normalizeDNSUpstreamPoolItems(items)
+	if len(items) == 0 {
+		items = dnsUpstreamPoolFromLegacy(loadDNSUpstreamsConfFile())
+	}
+	if err := saveDNSUpstreamPoolFile(items); err != nil {
+		return err
+	}
+	return saveDNSUpstreamsConfFile(dnsUpstreamPoolToLegacy(items))
+}