Return the moved card on PUT /:account_slug/cards/:card_number/board (#2849)

The JSON response was `204 No Content`, which forced clients to
make a follow-up GET to see the card on its new board. The Smithy
contract the SDKs are generated from already declares `MoveCard`
returns a Card, so the server was out of sync with the documented
shape.

Render `cards/show` for the JSON format so the response carries
the moved card (with the new `board` reference). The HTML format
is unchanged.

Added assertions on the returned body and added an API doc entry
for the endpoint, which was previously undocumented.

Author: robzolkos

app/controllers/cards/boards_controller.rb

@@ -14,7 +14,7 @@ def update
 
     respond_to do |format|
       format.html { redirect_to @card }
-      format.json { head :no_content }
+      format.json { render "cards/show" }
     end
   end
 

docs/api/sections/cards.md

@@ -251,6 +251,26 @@ __Response:__
 
 Returns `204 No Content` on success.
 
+## `PUT /:account_slug/cards/:card_number/board`
+
+Moves a card to a different board.
+
+| Parameter | Type | Required | Description |
+|-----------|------|----------|-------------|
+| `board_id` | string | Yes | The ID of the board to move the card to |
+
+__Request:__
+
+```json
+{
+  "board_id": "03f5v9zkft4hj9qq0lsn9ohcm"
+}
+```
+
+__Response:__
+
+Returns `200 OK` with the moved card in the same shape as `GET /:account_slug/cards/:card_number`. The `board` field reflects the new board.
+
 ## `POST /:account_slug/cards/:card_number/triage`
 
 Moves a card into a column.

test/controllers/cards/boards_controller_test.rb

@@ -26,7 +26,13 @@ class Cards::BoardsControllerTest < ActionDispatch::IntegrationTest
 
     put card_board_path(card), params: { board_id: new_board.id }, as: :json
 
-    assert_response :no_content
+    assert_response :success
     assert_equal new_board, card.reload.board
+
+    json = @response.parsed_body
+    assert_equal card.id, json["id"]
+    assert_equal card.number, json["number"]
+    assert_equal card.title, json["title"]
+    assert_equal new_board.id, json["board"]["id"]
   end
 end