message: skip unnecessary stringification
diff: @@ -7,15 +7,16 @@ const TOKEN_URL = 'https://www.bungie.net/platform/app/oauth/token/';
  export function getAccessTokenFromRefreshToken(refreshToken: Token): Promise<Tokens> {
  // https://github.com/zloirock/core-js/issues/178#issuecomment-192081350
  - return Promise.resolve(
  - fetch(TOKEN_URL, {
  - method: 'POST',
  - body: new URLSearchParams({
  + const body = new URLSearchParams({
  grant_type: 'refresh_token', // eslint-disable-line @typescript-eslint/naming-convention
  refresh_token: refreshToken.value, // eslint-disable-line @typescript-eslint/naming-convention
  client_id: oauthClientId(), // eslint-disable-line @typescript-eslint/naming-convention
  client_secret: oauthClientSecret(), // eslint-disable-line @typescript-eslint/naming-convention
  - }).toString(),
  + });
  + return Promise.resolve(
  + fetch(TOKEN_URL, {
  + method: 'POST',
  + body,
  headers: {
  'Content-Type': 'application/x-www-form-urlencoded',
  },
  @@ -26,15 +27,16 @@ export function getAccessTokenFromRefreshToken(refreshToken: Token): Promise<Tok
  }
  export function getAccessTokenFromCode(code: string): Promise<Tokens> {
  - return Promise.resolve(
  - fetch(TOKEN_URL, {
  - method: 'POST',
  - body: new URLSearchParams({
  + const body = new URLSearchParams({
  grant_type: 'authorization_code', // eslint-disable-line @typescript-eslint/naming-convention
  code,
  client_id: oauthClientId(), // eslint-disable-line @typescript-eslint/naming-convention
  client_secret: oauthClientSecret(), // eslint-disable-line @typescript-eslint/naming-convention
  - }).toString(),
  + });
  + return Promise.resolve(
  + fetch(TOKEN_URL, {
  + method: 'POST',
  + body,
  headers: {
  'Content-Type': 'application/x-www-form-urlencoded',
  },
  