chore: import upstream snapshot with attribution

wrapper/auth/metadata.go

@@ -0,0 +1,74 @@
+package auth
+
+import (
+	"errors"
+	"strings"
+
+	"go-micro.dev/v6/auth"
+	"go-micro.dev/v6/metadata"
+)
+
+const (
+	// MetadataKeyAuthorization is the key for the Authorization header in metadata
+	MetadataKeyAuthorization = "Authorization"
+	// BearerPrefix is the prefix for Bearer tokens
+	BearerPrefix = "Bearer "
+)
+
+var (
+	// ErrMissingToken is returned when no authorization token is found in metadata
+	ErrMissingToken = errors.New("missing authorization token in metadata")
+	// ErrInvalidToken is returned when the token format is invalid
+	ErrInvalidToken = errors.New("invalid token format, expected 'Bearer <token>'")
+)
+
+// TokenFromMetadata extracts the Bearer token from request metadata.
+// Returns the token string without the "Bearer " prefix, or an error if not found.
+func TokenFromMetadata(md metadata.Metadata) (string, error) {
+	// Check for Authorization header
+	authHeader, ok := md.Get(MetadataKeyAuthorization)
+	if !ok {
+		// Also check lowercase version
+		authHeader, ok = md.Get(strings.ToLower(MetadataKeyAuthorization))
+		if !ok {
+			return "", ErrMissingToken
+		}
+	}
+
+	// Verify Bearer prefix
+	if !strings.HasPrefix(authHeader, BearerPrefix) {
+		return "", ErrInvalidToken
+	}
+
+	// Extract token (remove "Bearer " prefix)
+	token := strings.TrimPrefix(authHeader, BearerPrefix)
+	if token == "" {
+		return "", ErrInvalidToken
+	}
+
+	return token, nil
+}
+
+// TokenToMetadata adds a Bearer token to metadata for outgoing requests.
+// The token should be provided without the "Bearer " prefix.
+func TokenToMetadata(md metadata.Metadata, token string) metadata.Metadata {
+	if md == nil {
+		md = metadata.Metadata{}
+	}
+
+	// Add Bearer prefix and set in metadata
+	md.Set(MetadataKeyAuthorization, BearerPrefix+token)
+	return md
+}
+
+// AccountFromMetadata extracts and verifies the token from metadata,
+// returning the associated account. This is a convenience function that
+// combines TokenFromMetadata and auth.Inspect.
+func AccountFromMetadata(md metadata.Metadata, a auth.Auth) (*auth.Account, error) {
+	token, err := TokenFromMetadata(md)
+	if err != nil {
+		return nil, err
+	}
+
+	return a.Inspect(token)
+}