Consider using await to reduce promise chaining

`node-fetch` [documentation](https://github.com/node-fetch/node-fetch#common-usage) recommends using `await` when calling `fetch`. I think this could be a good method to reduce the promise chaining we have in the `authorize` function.

Start by locating the authorize function and read node-fetch's linked common-usage documentation to compare its current promise handling with await-based usage. Done means the authorization behavior is preserved while promise chaining in authorize is reduced; verify the project's existing checks afterward.

Written by the indexing model from the issue text.