feat(notes): share a note with a person, not only through a project

Until now a note was shared exactly one way: file it in a shared project, and
everyone who could read the project could read the note. That is right when the
note belongs with a body of work and wrong when it is just "let Sofie see this" —
it made you stand up a project to hand over a single page.

A note can now be shared with named people directly, at viewer or editor — the
same two roles a project membership uses, so there is one idea of a role in the
program and not two. The paths stack: a note can be loose, filed, shared with
people, or any mix, and access is the most any of them allow.

The store:
  - note_shares (migration 0030): note ↔ user ↔ role, one row per person, owner
    recorded. Visibility (AllNotes, and search via mayTouchNote) widens to include
    notes shared directly with the reader.
  - the effective role folds a direct share on top of the owner and project paths.

The rules, drawn where they protect the owner:
  - read = viewer, edit text = editor, on any path.
  - MOVE a note (change its project) is owner-only: an editor filing it into a
    project the owner is not in would take the owner's own note away from them.
  - DELETE is owner or project-editor — a direct share, however high its role,
    does not reach to throwing the note away.
  - SHARE and UNSHARE are the owner's alone, like a project's invitations.
  - the picker is everyone on the instance (a closed, invited set) minus who is
    already on the note; a made-up id and the owner themselves are refused.

The list:
  - a "Delt med mig" group at the top, collapsible, that appears only when it has
    something in it — the same rule Favoritter follows — so it costs nothing when
    you share nothing. A shared note lives there, not also in a time bucket.
  - every shared note carries a small chip in its owner's avatar colour, the
    project mark's shape said for a person.
  - no star or archive button on a note somebody else owns: those change the note
    itself, and it is not yours to put away.
  - the editor grows a "Del med personer" panel for the owner: who can see it, at
    what role, and an add row drawn from the instance's other people.

The old comment in the notes footer argued against a note having an access list
of its own. That was the right call until the case it did not cover — sharing
without a project — turned out to be the one actually asked for. Updated to match.

Person now carries json tags, so a note's owner serialises as id/name/avatar_color
like every other person in the API rather than as Go field names.

Tests: a shared note reaches the other person marked and owned; a viewer reads but
cannot write; an editor writes but cannot re-share or delete; unshare removes
access and is owner-only; the candidate list excludes who is already on and the
owner; and a made-up id and self are refused. OpenAPI covers the three new routes.

Co-Authored-By: Claude Opus 5 <[email protected]>

internal/store/note_shares.go

@@ -0,0 +1,133 @@
+package store
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"time"
+)
+
+// NoteShare is one person's direct grant on a note: who they are, and what they
+// may do. The person is carried whole rather than by id, because every caller of
+// this wants to show them — a name and an avatar colour, never a bare id.
+type NoteShare struct {
+	User Person `json:"user"`
+	Role Role   `json:"role"`
+}
+
+// ShareNote grants a person a role on a note, or changes the role if they already
+// had one. The owner is passed so the row records who did the sharing; the caller
+// has already checked that they may.
+//
+// Sharing a note with its own owner is refused: the owner already has everything a
+// share could give, and a row saying otherwise is a contradiction waiting to
+// confuse the access check.
+func (db *DB) ShareNote(ctx context.Context, noteID, userID string, role Role, byUserID string) error {
+	if !role.Valid() || role == RoleOwner {
+		return errors.New("store: a note can be shared as viewer or editor")
+	}
+	var createdBy sql.NullString
+	if err := db.QueryRowContext(ctx,
+		`SELECT COALESCE(created_by, '') FROM notes WHERE id = ? AND deleted_at IS NULL`,
+		noteID).Scan(&createdBy.String); errors.Is(err, sql.ErrNoRows) {
+		return ErrNotFound
+	} else if err != nil {
+		return err
+	}
+	if createdBy.String == userID {
+		return errors.New("store: a note is already the owner's")
+	}
+	_, err := db.ExecContext(ctx, `
+		INSERT INTO note_shares (note_id, user_id, role, created_by, created_at)
+		VALUES (?, ?, ?, ?, ?)
+		ON CONFLICT (note_id, user_id) DO UPDATE SET role = excluded.role`,
+		noteID, userID, role, byUserID, time.Now().Unix())
+	return err
+}
+
+// UnshareNote removes a person's grant. Removing one that is not there is not an
+// error: the end state the caller asked for — this person cannot see this note —
+// is the same either way.
+func (db *DB) UnshareNote(ctx context.Context, noteID, userID string) error {
+	_, err := db.ExecContext(ctx,
+		`DELETE FROM note_shares WHERE note_id = ? AND user_id = ?`, noteID, userID)
+	return err
+}
+
+// ListNoteShares is who a note is shared with, each with their role, ordered by
+// name so the list under a note does not reshuffle every time it is opened.
+func (db *DB) ListNoteShares(ctx context.Context, noteID string) ([]NoteShare, error) {
+	rows, err := db.QueryContext(ctx, `
+		SELECT u.id, u.name, u.avatar_color, s.role
+		FROM note_shares s
+		JOIN users u ON u.id = s.user_id
+		WHERE s.note_id = ?
+		ORDER BY lower(u.name)`, noteID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var out []NoteShare
+	for rows.Next() {
+		var s NoteShare
+		if err := rows.Scan(&s.User.ID, &s.User.Name, &s.User.AvatarColor, &s.Role); err != nil {
+			return nil, err
+		}
+		out = append(out, s)
+	}
+	return out, rows.Err()
+}
+
+// NoteShareRole is the role a person holds on a note through a direct share, if
+// any. The bool is whether a share exists at all — distinct from a share whose
+// role could not be read — so a caller does not have to treat "no share" as an
+// error.
+func (db *DB) NoteShareRole(ctx context.Context, noteID, userID string) (Role, bool, error) {
+	var role Role
+	err := db.QueryRowContext(ctx,
+		`SELECT role FROM note_shares WHERE note_id = ? AND user_id = ?`, noteID, userID).Scan(&role)
+	if errors.Is(err, sql.ErrNoRows) {
+		return "", false, nil
+	}
+	if err != nil {
+		return "", false, err
+	}
+	if !role.Valid() {
+		// A role the database holds but this build does not understand is no access,
+		// never a guess — the same rule project roles follow.
+		return "", false, nil
+	}
+	return role, true, nil
+}
+
+// NotesSharedWith returns the ids, among those given, that are shared directly with
+// the user. It answers the Delt med mig question in one query rather than one per
+// note, and takes the ids it is scoping so it never has to load a person's whole
+// world to mark a single page.
+func (db *DB) NotesSharedWith(ctx context.Context, userID string, noteIDs []string) (map[string]bool, error) {
+	out := map[string]bool{}
+	if len(noteIDs) == 0 {
+		return out, nil
+	}
+	args := make([]any, 0, len(noteIDs)+1)
+	args = append(args, userID)
+	for _, id := range noteIDs {
+		args = append(args, id)
+	}
+	rows, err := db.QueryContext(ctx,
+		`SELECT note_id FROM note_shares WHERE user_id = ? AND note_id IN (`+placeholders(len(noteIDs))+`)`,
+		args...)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var id string
+		if err := rows.Scan(&id); err != nil {
+			return nil, err
+		}
+		out[id] = true
+	}
+	return out, rows.Err()
+}