Document code-style for enums and class constants

Author: derrabus

contributing/code/standards.rst

@@ -210,8 +210,12 @@ Naming Conventions
 * Use `snake_case`_ for configuration parameters and Twig template variables
  (e.g. ``framework.csrf_protection``, ``http_status_code``);
 
-* Use namespaces for all PHP classes and `UpperCamelCase`_ for their names (e.g.
- ``ConsoleLogger``);
+* Use `SCREAMING_SNAKE_CASE`_ for constants (e.g. ``InputArgument::IS_ARRAY``);
+
+* Use `UpperCamelCase`_ for enumeration cases (e.g. ``InputArgumentMode::IsArray``);
+
+* Use namespaces for all PHP classes, interfaces, traits and enums and
+ `UpperCamelCase`_ for their names (e.g. ``ConsoleLogger``);
 
 * Prefix all abstract classes with ``Abstract`` except PHPUnit ``*TestCase``.
  Please note some early Symfony classes do not follow this convention and
@@ -222,6 +226,9 @@ Naming Conventions
 
 * Suffix traits with ``Trait``;
 
+* Don't use a dedicated suffix for classes or enumerations (e.g. like ``Class``
+ or ``Enum``), except for the cases listed below.
+
 * Suffix exceptions with ``Exception``;
 
 * Prefix PHP attributes with ``As`` where applicable (e.g. ``#[AsCommand]``