Wrap comment params for flat JSON payloads (#2679)

* Wrap comment params for flat JSON payloads

The SDK sends flat JSON ({"body": "..."}) but Rails wrap_parameters
auto-detection misses :body since it's a virtual ActionText attribute,
not in Comment.attribute_names. Explicitly declare wrap_parameters so
params.expect(comment: [...]) works with both wrapped and flat payloads.

* Test comment create and update with flat JSON params

test/controllers/cards/comments_controller_test.rb

@@ -84,6 +84,26 @@ class Cards::CommentsControllerTest < ActionDispatch::IntegrationTest
     assert_equal card_comment_url(comment.card, comment), @response.parsed_body["url"]
   end
 
+  test "create as JSON with flat params" do
+    card = cards(:logo)
+
+    assert_difference -> { card.comments.count }, +1 do
+      post card_comments_path(card), params: { body: "Flat comment" }, as: :json
+    end
+
+    assert_response :created
+    assert_equal "Flat comment", Comment.last.body.to_plain_text
+  end
+
+  test "update as JSON with flat params" do
+    comment = comments(:logo_agreement_kevin)
+
+    put card_comment_path(cards(:logo), comment), params: { body: "Flat update" }, as: :json
+
+    assert_response :success
+    assert_equal "Flat update", comment.reload.body.to_plain_text
+  end
+
   test "update as JSON" do
     comment = comments(:logo_agreement_kevin)