Implement the POST /api/opening endpoint

[programarivm]

This endpoint is intended to fetch chess opening data given a set of parameters.

Method	Endpoint	Description
POST	/api/opening	Returns chess opening data.

Parameter	Type	Description	Optional
eco	string	ECO code.	Yes
name	string	Opening name.	Yes
movetext	string	Movetext.	Yes

Response	Description
200 (OK)	The chess opening is valid.
204 (No Content)	The chess opening was found in the database.

Query examples:

curl -d '{"eco":"B94"}' -H "Content-Type: application/json" -X POST http://localhost:8000/api/opening

Response:

{
  "eco": "B94",
  "name": "Sicilian Defense: Najdorf Variation",
  "movetext": "1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Bg5"
}

The POST /api/opening endpoint should be implemented in a new file called src/Controller/OpeningController.php.