refactor(user): share user-search logic between v1 and v2

Extract the duplicated user-search business logic into two helpers both API
versions call, and refactor v1's handlers onto them:
- user.SearchUsers wraps ListUsers + email obfuscation (global search)
- models.SearchUsersForProject wraps the project read check + ListUsersFromProject

Each handler keeps its own forbidden mapping (v1 echo.ErrForbidden vs v2
huma) so v1 stays byte-identical on the wire.

pkg/models/user_project.go

@@ -18,10 +18,30 @@ package models
 
 import (
 	"code.vikunja.io/api/pkg/user"
+	"code.vikunja.io/api/pkg/web"
 	"xorm.io/builder"
 	"xorm.io/xorm"
 )
 
+// SearchUsersForProject performs the per-project user search shared by both API
+// versions: it checks the caller can read the project, then lists the users
+// with access to it. canRead is false (with no error) when the caller lacks
+// read access, so each handler can map that to its own forbidden response.
+func SearchUsersForProject(s *xorm.Session, project *Project, a web.Auth, currentUser *user.User, search string) (users []*user.User, canRead bool, err error) {
+	canRead, _, err = project.CanRead(s, a)
+	if err != nil {
+		return nil, false, err
+	}
+	if !canRead {
+		return nil, false, nil
+	}
+	users, err = ListUsersFromProject(s, project, currentUser, search)
+	if err != nil {
+		return nil, true, err
+	}
+	return users, true, nil
+}
+
 // ProjectUIDs hold all kinds of user IDs from accounts who have access to a project
 type ProjectUIDs struct {
 	ProjectOwnerID    int64 `xorm:"projectOwner"`

pkg/routes/api/v1/user_list.go

@@ -52,17 +52,12 @@ func UserList(c *echo.Context) error {
 		return err
 	}
 
-	users, err := user.ListUsers(s, search, currentUser, nil)
+	users, err := user.SearchUsers(s, search, currentUser)
 	if err != nil {
 		_ = s.Rollback()
 		return err
 	}
 
-	// Obfuscate the mailadresses
-	for in := range users {
-		users[in].Email = ""
-	}
-
 	return c.JSON(http.StatusOK, users)
 }
 
@@ -98,15 +93,6 @@ func ListUsersForProject(c *echo.Context) error {
 	s := db.NewSession()
 	defer s.Close()
 
-	canRead, _, err := project.CanRead(s, auth)
-	if err != nil {
-		_ = s.Rollback()
-		return err
-	}
-	if !canRead {
-		return echo.ErrForbidden
-	}
-
 	currentUser, err := user.GetCurrentUser(c)
 	if err != nil {
 		_ = s.Rollback()
@@ -114,11 +100,14 @@ func ListUsersForProject(c *echo.Context) error {
 	}
 
 	search := c.QueryParam("s")
-	users, err := models.ListUsersFromProject(s, &project, currentUser, search)
+	users, canRead, err := models.SearchUsersForProject(s, &project, auth, currentUser, search)
 	if err != nil {
 		_ = s.Rollback()
 		return err
 	}
+	if !canRead {
+		return echo.ErrForbidden
+	}
 
 	if err := s.Commit(); err != nil {
 		_ = s.Rollback()

pkg/routes/api/v2/user_search.go

@@ -72,7 +72,7 @@ func usersSearch(ctx context.Context, in *struct {
 		return nil, translateDomainError(err)
 	}
 
-	users, err := user.ListUsers(s, in.Q, currentUser, nil)
+	users, err := user.SearchUsers(s, in.Q, currentUser)
 	if err != nil {
 		_ = s.Rollback()
 		return nil, translateDomainError(err)
@@ -81,10 +81,6 @@ func usersSearch(ctx context.Context, in *struct {
 		return nil, translateDomainError(err)
 	}
 
-	for i := range users {
-		users[i].Email = ""
-	}
-
 	return &userListBody{Body: NewPaginated(users, int64(len(users)), 1, len(users))}, nil
 }
 
@@ -100,8 +96,14 @@ func projectUsersSearch(ctx context.Context, in *struct {
 	s := db.NewSession()
 	defer s.Close()
 
+	currentUser, err := models.GetUserOrLinkShareUser(s, a)
+	if err != nil {
+		_ = s.Rollback()
+		return nil, translateDomainError(err)
+	}
+
 	project := &models.Project{ID: in.ProjectID}
-	canRead, _, err := project.CanRead(s, a)
+	users, canRead, err := models.SearchUsersForProject(s, project, a, currentUser, in.Q)
 	if err != nil {
 		_ = s.Rollback()
 		return nil, translateDomainError(err)
@@ -110,18 +112,6 @@ func projectUsersSearch(ctx context.Context, in *struct {
 		_ = s.Rollback()
 		return nil, huma.Error403Forbidden("forbidden")
 	}
-
-	currentUser, err := models.GetUserOrLinkShareUser(s, a)
-	if err != nil {
-		_ = s.Rollback()
-		return nil, translateDomainError(err)
-	}
-
-	users, err := models.ListUsersFromProject(s, project, currentUser, in.Q)
-	if err != nil {
-		_ = s.Rollback()
-		return nil, translateDomainError(err)
-	}
 	if err := s.Commit(); err != nil {
 		return nil, translateDomainError(err)
 	}

pkg/user/users_project.go

@@ -34,6 +34,20 @@ type ProjectUserOpts struct {
 	MatchFuzzily                bool
 }
 
+// SearchUsers performs the global user search shared by both API versions:
+// it lists users matching the search string and obfuscates their email
+// addresses before returning.
+func SearchUsers(s *xorm.Session, search string, currentUser *User) (users []*User, err error) {
+	users, err = ListUsers(s, search, currentUser, nil)
+	if err != nil {
+		return nil, err
+	}
+	for i := range users {
+		users[i].Email = ""
+	}
+	return users, nil
+}
+
 // ListUsers returns a list with all users, filtered by an optional search string
 func ListUsers(s *xorm.Session, search string, currentUser *User, opts *ProjectUserOpts) (users []*User, err error) {
 	if opts == nil {