[core] Add make_name_with_suffix helper to optimize string concatenation

esphome/config_validation.py

@@ -1195,6 +1195,13 @@ def validate_bytes(value):
 
 
 def hostname(value):
+    """Validate that the value is a valid hostname.
+
+    Maximum length is 63 characters per RFC 1035.
+
+    Note: If this limit is changed, update MAX_NAME_WITH_SUFFIX_SIZE in
+    esphome/core/application.h to accommodate the new maximum length.
+    """
     value = string(value)
     if re.match(r"^[a-z0-9-]{1,63}$", value, re.IGNORECASE) is not None:
         return value