[GITEA] enable system users search via the API

Refs: https://codeberg.org/forgejo/forgejo/issues/1403
(cherry picked from commit 87bd40411e)

Conflicts:
	routers/api/v1/user/user.go
	https://codeberg.org/forgejo/forgejo/pulls/1469
(cherry picked from commit 74f70ca873)
(cherry picked from commit 673a75bb43)
(cherry picked from commit fcd4535ac6)
(cherry picked from commit 56b229f22e)
(cherry picked from commit 45b922ae76)
(cherry picked from commit 03805f3bf4)
(cherry picked from commit 16c67f70d5)
(cherry picked from commit 1b862a14ad)
(cherry picked from commit 4a5cdcf649)

routers/api/v1/user/user.go

@@ -54,19 +54,33 @@ func Search(ctx *context.APIContext) {
 
 	listOptions := utils.GetListOptions(ctx)
 
-	users, maxResults, err := user_model.SearchUsers(ctx, &user_model.SearchUserOptions{
-		Actor:       ctx.Doer,
-		Keyword:     ctx.FormTrim("q"),
-		UID:         ctx.FormInt64("uid"),
-		Type:        user_model.UserTypeIndividual,
-		ListOptions: listOptions,
-	})
-	if err != nil {
-		ctx.JSON(http.StatusInternalServerError, map[string]any{
-			"ok":    false,
-			"error": err.Error(),
+	uid := ctx.FormInt64("uid")
+	var users []*user_model.User
+	var maxResults int64
+	var err error
+
+	switch uid {
+	case user_model.GhostUserID:
+		maxResults = 1
+		users = []*user_model.User{user_model.NewGhostUser()}
+	case user_model.ActionsUserID:
+		maxResults = 1
+		users = []*user_model.User{user_model.NewActionsUser()}
+	default:
+		users, maxResults, err = user_model.SearchUsers(ctx, &user_model.SearchUserOptions{
+			Actor:       ctx.Doer,
+			Keyword:     ctx.FormTrim("q"),
+			UID:         uid,
+			Type:        user_model.UserTypeIndividual,
+			ListOptions: listOptions,
 		})
-		return
+		if err != nil {
+			ctx.JSON(http.StatusInternalServerError, map[string]any{
+				"ok":    false,
+				"error": err.Error(),
+			})
+			return
+		}
 	}
 
 	ctx.SetLinkHeader(int(maxResults), listOptions.PageSize)