fix(checkins): read error message from response body

[subzero10]

Status

READY

Description

Fixes #223.
Read error messages from response body instead of relying only on the HTTP status code.

This should handle the cases where a more specific message is included in the response body.
For example, we would show a generic The API key provided is invalid. when receiving a 403, but there are cases where the message could be:

• either You need to upgrade your plan to get cron support.
• or You have reached your plan's limit for the number of check-ins.

[subzero10]

@stympy I am facing another issue here and I'd like your input on how to go about it:
I'm getting 429 errors if I create checkins in a for loop:

php artisan honeybadger:checkins:sync
string(29) "08:38:06: fetching project id"
string(46) "08:38:07: fetching check-ins for project 68958"
string(54) "08:38:07: creating check-in sync-all for project 68958"
string(58) "08:38:08: creating check-in check-uptime for project 68958"
[2025-01-07 08:38:08] local.ERROR: You have hit your exception rate limit. {"exception":"[object] (Honeybadger\\Exceptions\\ServiceException(code: 0): You have hit your exception rate limit

I verified that if I wait 1 second (sleep(1)), I don't get the error.
Could this be because the personal API token is stricter in terms of rate limitations?

Also, when I first implemented this feature I wouldn't get this error, and I remember specifically creating the maximum number of checkins allowed in my account (5). Now I get the error at the moment it tries to create the second one.