minor #7766 [Form] Added a small explanation about named forms (iltar, javiereguiluz)

This PR was merged into the 2.7 branch.

Discussion
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[Form] Added a small explanation about named forms

I've added a small explanation on how to add the same form multiple times to the same page, by using named forms. Should fix #4090.

Note that this feature was already added in at least one of the patches in 2.1.

Commits
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8d246c4 Minor reword
e0137f5 Added a note about named form types

Author: javiereguiluz

forms.rst

@@ -703,6 +703,13 @@ the choice is ultimately up to you.
 
         $form->get('agreeTerms')->setData(true);
 
+
+.. note::
+
+    The form name is automatically generated from the type class name. If you want
+    to modify it, use the :method:`Symfony\\Component\\Form\\FormFactoryInterface::createNamed` method.
+    You can even suppress the name completely by setting it to an empty string.
+
 Final Thoughts
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