feat(server): role based authentication system (#2434)

- Parse toml configuration file, see https://github.com/qdm12/gluetun-wiki/blob/main/setup/advanced/control-server.md#authentication
- Retro-compatible with existing AND documented routes, until after v3.41 release
- Log a warning if an unprotected-by-default route is accessed unprotected
- Authentication methods: none, apikey, basic
- `genkey` command to generate API keys

Co-authored-by: Joe Jose <45399349+joejose97@users.noreply.github.com>

internal/server/middlewares/auth/apikey.go

@@ -0,0 +1,36 @@
+package auth
+
+import (
+	"crypto/sha256"
+	"crypto/subtle"
+	"net/http"
+)
+
+type apiKeyMethod struct {
+	apiKeyDigest [32]byte
+}
+
+func newAPIKeyMethod(apiKey string) *apiKeyMethod {
+	return &apiKeyMethod{
+		apiKeyDigest: sha256.Sum256([]byte(apiKey)),
+	}
+}
+
+// equal returns true if another auth checker is equal.
+// This is used to deduplicate checkers for a particular route.
+func (a *apiKeyMethod) equal(other authorizationChecker) bool {
+	otherTokenMethod, ok := other.(*apiKeyMethod)
+	if !ok {
+		return false
+	}
+	return a.apiKeyDigest == otherTokenMethod.apiKeyDigest
+}
+
+func (a *apiKeyMethod) isAuthorized(_ http.Header, request *http.Request) bool {
+	xAPIKey := request.Header.Get("X-API-Key")
+	if xAPIKey == "" {
+		xAPIKey = request.URL.Query().Get("api_key")
+	}
+	xAPIKeyDigest := sha256.Sum256([]byte(xAPIKey))
+	return subtle.ConstantTimeCompare(xAPIKeyDigest[:], a.apiKeyDigest[:]) == 1
+}