schema REFACTOR lysc_is_* functions

- rewrite lysc_is_userordered() as macro
- add lysc_is_key() (as macro)
diff --git a/src/tree_schema.h b/src/tree_schema.h
index 882fe2f..cb2489e 100644
--- a/src/tree_schema.h
+++ b/src/tree_schema.h
@@ -1742,6 +1742,24 @@
 };
 
 /**
+ * @brief Examine whether a node is user-ordered list or leaf-list.
+ *
+ * @param[in] lysc_node Schema node to examine.
+ * @return Boolean value whether the @p node is user-ordered or not.
+ */
+#define lysc_is_userordered(lysc_node) \
+    ((!lysc_node || !(lysc_node->nodetype & (LYS_LEAFLIST | LYS_LIST)) || !(lysc_node->flags & LYS_ORDBY_USER)) ? 0 : 1)
+
+/**
+ * @brief Examine whether a node is a list's key.
+ *
+ * @param[in] lysc_node Schema node to examine.
+ * @return Boolean value whether the @p node is a key or not.
+ */
+#define lysc_is_key(lysc_node) \
+    ((!lysc_node || !(lysc_node->nodetype & (LYS_LEAF)) || !(lysc_node->flags & LYS_KEY)) ? 0 : 1)
+
+/**
  * @brief Get the groupings sized array of the given (parsed) schema node.
  * Decides the node's type and in case it has a groupings array, returns it.
  * @param[in] node Node to examine.
@@ -1872,15 +1890,6 @@
 LY_ERR lysc_module_dfs_full(const struct lys_module *mod, lysc_dfs_clb dfs_clb, void *data);
 
 /**
- * @brief Examine whether a node is user-ordered list or leaf-list.
- *
- * @param[in] schema Schema node to examine.
- * @return non-zero if it is,
- * @return Boolean value whether the @p node is user-ordered or not.
- */
-ly_bool lysc_is_userordered(const struct lysc_node *schema);
-
-/**
  * @brief Set a schema private pointer to a user pointer.
  *
  * @param[in] node Node, whose private field will be assigned. Works also for RPCs, actions, and notifications.
diff --git a/src/tree_schema_helpers.c b/src/tree_schema_helpers.c
index 42743f0..65d698c 100644
--- a/src/tree_schema_helpers.c
+++ b/src/tree_schema_helpers.c
@@ -1627,12 +1627,3 @@
     return 0;
 }
 
-API ly_bool
-lysc_is_userordered(const struct lysc_node *schema)
-{
-    if (!schema || !(schema->nodetype & (LYS_LEAFLIST | LYS_LIST)) || !(schema->flags & LYS_ORDBY_USER)) {
-        return 0;
-    }
-
-    return 1;
-}