Remove pagination from context (#807)

Pagination related flags now write directly to ListOption struct and enforce non negative numbers.
Flag tests were added to cover the validation

Reviewed-on: https://gitea.com/gitea/tea/pulls/807
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: TheFox0x7 <thefox0x7@gmail.com>
Co-committed-by: TheFox0x7 <thefox0x7@gmail.com>

cmd/admin/users/list.go

@@ -43,7 +43,7 @@ func RunUserList(_ stdctx.Context, cmd *cli.Command) error {
 
 	client := ctx.Login.Client()
 	users, _, err := client.AdminListUsers(gitea.AdminListUsersOptions{
-		ListOptions: ctx.GetListOptions(),
+		ListOptions: flags.GetListOptions(),
 	})
 	if err != nil {
 		return err