Add missing 5.4 migration guide entries

- Component-alias/default-table collision warning
- PSR-13 link support on Response
- New collection helpers: keys(), values(), implode(), when(), unless()

Author: dereuromark

docs/en/appendices/5-4-migration-guide.md

@@ -27,6 +27,27 @@ The default eager loading strategy for `HasMany` and `BelongsToMany` association
 has changed from `select` to `subquery`. If you need the previous behavior,
 explicitly set `'strategy' => 'select'` when defining associations.
 
+### Controller
+
+When loading a component that has the same alias as the controller's default table,
+CakePHP now triggers a warning. This helps identify situations where accessing
+`$this->ComponentAlias` returns the table instead of the component:
+
+```php
+class PaymentsController extends AppController
+{
+    public function initialize(): void
+    {
+        parent::initialize();
+        // Triggers warning: Component alias `Payments` clashes with the default table name
+        $this->loadComponent('Payments');
+    }
+}
+```
+
+To resolve this, either use a different component alias or set `Controller::$defaultTable`
+to an empty string if the controller doesn't use a table.
+
 ## Deprecations
 
 - WIP
@@ -60,12 +81,60 @@ explicitly set `'strategy' => 'select'` when defining associations.
   nested array format matching `contain()` syntax.
   See [Converting Request Data into Entities](../orm/saving-data#converting-request-data-into-entities).
 
+### Http
+
+- Added PSR-13 Link implementation with `Cake\Http\Link\Link` and `Cake\Http\Link\LinkProvider`
+  classes for hypermedia link support. Links added to responses are automatically emitted
+  as HTTP `Link` headers.
+
+```php
+use Cake\Http\Link\Link;
+
+// Add links to a response
+$response = $response->withLink(new Link('/api/users', 'self'));
+$response = $response->withLink(
+    (new Link('/api/users?page=2'))
+        ->withRel('next')
+        ->withAttribute('type', 'application/json'),
+);
+
+// Preload resources
+$response = $response->withLink(
+    (new Link('/css/app.css'))
+        ->withRel('preload')
+        ->withAttribute('as', 'style'),
+);
+```
+
 ### Utility
 
 - Added `Cake\Utility\Fs\Finder` class for fluent file discovery with pattern matching,
   depth control, and custom filters. Added `Cake\Utility\Fs\Path` for cross-platform
   path manipulation.
 
+### Collection
+
+- Added `keys()` method to return a collection containing only the keys.
+- Added `values()` method to return a collection of values re-indexed with consecutive integers.
+- Added `implode()` method to concatenate elements into a string, with optional path extraction.
+- Added `when()` and `unless()` methods for conditional method chaining.
+
+```php
+// keys() and values()
+$collection = new Collection(['a' => 1, 'b' => 2]);
+$collection->keys()->toList(); // ['a', 'b']
+$collection->values()->toList(); // [1, 2]
+
+// implode() with path extraction
+$collection = new Collection([['name' => 'foo'], ['name' => 'bar']]);
+$collection->implode(', ', 'name'); // 'foo, bar'
+
+// Conditional chaining with when() and unless()
+$collection = new Collection($items)
+    ->when($shouldFilter, fn($c) => $c->filter(fn($v) => $v['active']))
+    ->unless($hasDefaults, fn($c) => $c->append($defaults));
+```
+
 ### View
 
 - Added `{{inputId}}` template variable to `inputContainer` and `error` templates