Style proposal: async/await vs .then()

I've seen there's a mix in the code where sometimes `async/await` is used and sometimes `somePromise.then().catch()`. I'd like to propose to homogenize the code by using *always* `async/await`, and I offer myself to make the PR should the proposal be accepted.

Also, if it's accepted, it should be added to the contribution guideline.

The issue does not identify specific files or tests. First review the existing async/await and .then().catch() usage across the codebase, then check the contribution guideline. Done means agreeing on a convention, applying it consistently, and documenting the accepted style.

Written by the indexing model from the issue text.