propagate panics as errors to callers

[2bndy5]

Currently, there are a lot of places where I use Result.expect() to panic on unexpected behavior. Most notably in RestApiClient.send_api_request(). It is more idiomatic rust to handle errors in the caller instead of arbitrarily throwing panics.

This solution may be considered a refactor since there are so many instances where the code calls Result.expect(), or Result.unwrap() (same as .expect() but without customized error message).

Note

There are some instances where it makes sense to use .unwrap(), but it should be determined by the code block's local context.

TBH, this problem was born from the fact that this is my first rust project. I should have picked a more robust design from the start.