fix(api): return 4xx for invalid fork repository names (#39909)

Fixes #39908

---------

Signed-off-by: Ferdinand-MZ <ferdinandmaulanazafauzi@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/api/v1/repo/fork.go

@@ -12,7 +12,6 @@ import (
 	"gitea.dev/models/perm"
 	access_model "gitea.dev/models/perm/access"
 	repo_model "gitea.dev/models/repo"
-	user_model "gitea.dev/models/user"
 	"gitea.dev/modules/optional"
 	api "gitea.dev/modules/structs"
 	"gitea.dev/modules/util"
@@ -166,13 +165,7 @@ func CreateFork(ctx *context.APIContext) {
 		Description: repo.Description,
 	})
 	if err != nil {
-		if errors.Is(err, util.ErrAlreadyExist) || repo_model.IsErrReachLimitOfRepo(err) {
-			ctx.APIError(http.StatusConflict, err.Error())
-		} else if errors.Is(err, user_model.ErrBlockedUser) {
-			ctx.APIError(http.StatusForbidden, err.Error())
-		} else {
-			ctx.APIErrorInternal(err)
-		}
+		ctx.APIErrorAuto(err)
 		return
 	}