Add user-defined literal to create a nametag provider from a string literal

docs/names.md

@@ -98,6 +98,12 @@ When used with C++26 and reflection support, the library offers another overload
 // rename entities.
 foo.as<"left">();             // tab_foo AS left
 max(left.id).as<"max_id">();  // MAX(left.id) AS max_id
+
+// alternatively you can use the user-defined literal "_alias" instead of template arguments.
+using namespace sqlpp::literals;  // using namespace required in scope
+
+foo.as("left"_alias);             // tab_foo AS left
+max(left.id).as("max_id"_alias);  // MAX(left.id) AS max_id
 ```
 
 **Experimental**

include/sqlpp23/core/name/create_reflection_name_tag.h

@@ -93,4 +93,12 @@ consteval auto make_alias() -> ::sqlpp::meta::reflection_alias<Alias> {
 }
 
 }  // namespace sqlpp::meta
+
+namespace sqlpp::literals {
+template <::sqlpp::detail::fixed_string Alias>
+consteval auto operator""_alias() -> ::sqlpp::meta::reflection_alias<Alias> {
+  return {};
+}
+
+}  // namespace sqlpp::literals
 #endif

tests/core/meta/alias.cpp

@@ -28,17 +28,19 @@
 
 int main(int, char*[]) {
 #if SQLPP_INCLUDE_REFLECTION == 1
+  using namespace sqlpp::literals;
+
   const auto foo = test::TabFoo{};
   const auto bar = test::TabBar{};
 
   SQLPP_COMPARE(avg(bar.id + 7).as<"my_average">(),
                 "AVG(tab_bar.id + 7) AS my_average");
 
   const auto table_a = foo.as<"table_a">();
-  const auto table_b = bar.as<"table_b">();
+  const auto table_b = bar.as("table_b"_alias);
 
   SQLPP_COMPARE(sqlpp::select(table_a.id.as<"id_a">(), table_a.intN,
-                              table_b.id.as<"id_b">(), table_b.textN)
+                              table_b.id.as("id_b"_alias), table_b.textN)
                     .from(table_a.join(table_b).on(table_a.id == table_b.id)),
                 "SELECT table_a.id AS id_a, table_a.int_n, table_b.id AS id_b, "
                 "table_b.text_n "