Throw exceptions instead of the ugly Result monad

[christopher-dG]

Closes #12, ref #22

I cherry-picked c6bbc7b and it seems to have not bitrotted. In case it's not obvious, this is totally breaking (but consistently so, so updates shouldn't be very difficult).

The gist is: instead of receiving a Result{T} that contains a T (repo, user, PR, etc.), an HTTP response, and exception info, we get back a Tuple{T, Response}. If an exception was thrown in the request, it's thrown to the user too, they can catch it like any other error-handling situation. There's HTTPError is anything that was thrown from HTTP.request, PostProcessorError which generally comes from parsing, and RateLimitedError, which is not new.

Code changes might look like:

# Let's be real, no one actually checks for errors
gh = GitHubAPI(ENV["GITHUB_TOKEN"])

# Before:
resp = get_user(gh)
me = GitForge.value(resp)

# After:
me, _ = get_user(gh)

# Okay, maybe some people do check for errors and such

# Before:
resp = get_user(gh)
if GitForge.exception(resp) !== nothing
    @warn "ahhhh!!!" ex
    return
end
@info "Not rate limited yet" remaining=HTTP.header(GitForge.response(resp), "X-Ratelimit-Remaining")
me = GitForge.value(resp)

# After:
try
    me, resp = get_user(gh)
    @info "Not rate limited yet" remaining=HTTP.header(resp, "X-Ratelimit-Remaining")
catch e
    @warn "ahhhh!!!" ex=(e, catch_backtrace())
end

IMO it just makes a lot more intuitive sense.

TODO: need to update CI to GHA, update Documenter setup and manifest, bump minor version.

[oxinabox]

I think think this makes more sense.
Use the idioms of the language we are using.
Sometimes there are good reasons for varying this.
But standard REST/CRUD isn't one of them.

How much does this break downstream, e.g. registrstor?
I guess a lot.
OTOH project.toml compat means it can stay on old version forever

[christopher-dG]

OTOH project.toml compat means it can stay on old version forever

Yeah, I think we can just rely on compat here.