Add expression-based conditions to enable or disable Twig hookables

[loic425]

Introduce a new 'condition' configuration option for hookables. The value is an Expression Language expression prefixed with '@=' that is evaluated at runtime against the hook context. The hookable is rendered only when the expression returns true.

Conditions are linted at the application boot to fail fast on invalid expressions, and evaluated by a new HookableConditionChecker injected into the HookRenderer. 'enabled' remains a static boot-time flag, keeping the two mechanisms clearly separated.

[diimpp]

This defined early return essentially disables lint for older than SF 7.1.

::IGNORE_UNKNOWN_VARIABLES was introduced in 7.1 and only changes method signature, not behaviour. Previosly we should have supplied null for the same result.

So something like this instead of early return.

-            $expressionLanguage->lint(substr($condition, 2), [], Parser::IGNORE_UNKNOWN_VARIABLES);
+            $expression = substr($condition, 2);
+
+            if (defined(Parser::class . '::IGNORE_UNKNOWN_VARIABLES')) {
+                $expressionLanguage->lint(
+                    $expression,
+                    [],
+                    Parser::IGNORE_UNKNOWN_VARIABLES
+                );
+            } else {
+                $expressionLanguage->lint(
+                    $expression,
+                    null
+                );
+            }

symfony/expression-language@684ac49#diff-1a7c1850f88287936713a7072af9331818e14581fc71feed100c41e1747593ceR37-L103

[loic425]

I agree, but I think we still need the "try/catch" to have a better error.