spotify.dev, as data

#### ResponseIf the user accepts your request, then the user is redirected back to theapplication using the `redirect_uri` passed on the authorized request describedThe callback contains two query parameters:An authorization code that can be exchanged for an access token.The value of the `state` parameter supplied in the request.https://my-domain.com/callback?code=NApCCg..BkWtQ&state=34fFs29kd09If the user does not accept your request or if an error has occurred, the responsequery string contains the following parameters:The reason authorization failed, for example: "access_denied"https://my-domain.com/callback?error=access_denied&state=34fFs29kd09In both cases, your app should compare the `state` parameter that it receivedin the redirection URI with the state parameter it originally provided toSpotify in the authorization URI. If there is a mismatch then your app shouldreject the request and stop the authentication flow.## Request an access tokenIf the user accepted your request, then your app is ready to exchange theauthorization code for an access token. It can do this by sending a `POST`request to the `/api/token` endpoint.The body of this `POST` request must contain the following parameters encodedin `application/x-www-form-urlencoded`:This field must contain the value `"authorization_code"`.The authorization code returned from the previous request.This parameter is used for validation only (there is no actual redirection). The value of this parameter must exactly match the value of `redirect_uri` supplied when requesting the authorization code.The request must include the following HTTP headers:Base 64 encoded string that contains the client ID and client secret key. The field must have the format: `Authorization: Basic <base64 encoded client_id:client_secret>`Set to `application/x-www-form-urlencoded`.This step is usually implemented within the callback described on the request