Add session-bound personal profile editing

auth/profile.go

@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: MPL-2.0
+
+package auth
+
+import (
+	"context"
+	"errors"
+	"strings"
+	"time"
+	"unicode"
+	"unicode/utf8"
+)
+
+var (
+	ErrProfileInput        = errors.New("auth: invalid profile change")
+	ErrProfileAccess       = errors.New("auth: profile session is unavailable")
+	ErrProfileConflict     = errors.New("auth: profile changed; reload before editing")
+	ErrUsernameUnavailable = errors.New("auth: username is unavailable")
+)
+
+// OwnProfile contains mutable identity, not credentials or organization roles.
+// Revision is independent of timestamps and increases for every profile edit.
+type OwnProfile struct {
+	UserID, Username, Email, DisplayName string
+	Revision                             int64
+}
+
+// ProfileEdit is a trusted repository command, not an HTTP input model. The
+// application must authenticate the session, validate CSRF/origin and rate-limit
+// mutations. Username edits additionally require recent reauthentication (and
+// any account-specific MFA). For password reauthentication, supply the verified
+// hash so a concurrent password reset invalidates the write. After verified
+// passkey approval, leave it empty. Do not log or serialize this command.
+type ProfileEdit struct {
+	UserID               string
+	SessionDigest        [32]byte
+	ExpectedRevision     int64
+	Field, Value         string
+	ExpectedPasswordHash string
+}
+
+// NormalizeProfileValue validates only supported fields. Email is deliberately
+// absent: verified mailbox changes need a separate pending/confirmation flow.
+func NormalizeProfileValue(field, value string) (string, error) {
+	value = strings.TrimSpace(value)
+	switch field {
+	case "username":
+		if !identifierPattern.MatchString(value) {
+			return "", ErrProfileInput
+		}
+	case "display_name":
+		if value == "" || len(value) > 128 || !utf8.ValidString(value) {
+			return "", ErrProfileInput
+		}
+		for _, r := range value {
+			if unicode.IsControl(r) {
+				return "", ErrProfileInput
+			}
+		}
+	default:
+		return "", ErrProfileInput
+	}
+	return value, nil
+}
+
+// OwnProfileRepository is optional; no change to the authentication Repository
+// interface is required. It derives access from the current session, never from
+// a site-wide administrator flag. Implementations atomically recheck identity,
+// session and revision, mutate one field, and append the audit. Username edits
+// revoke other sessions but preserve the acting session. They never reassign
+// stable IDs, memberships, passkeys, billing identities or historical records.
+type OwnProfileRepository interface {
+	OwnProfile(context.Context, [32]byte, time.Time) (OwnProfile, error)
+	UpdateOwnProfile(context.Context, ProfileEdit, AuditEvent) (OwnProfile, error)
+}