Clear names for receivers API fields

[santihernandezc]

We're using lastNotify and lastNotifyDuration to indicate the time and duration for the last attempt regardless of the outcome. A better option would be to use lastAttempt and lastAttemptDuration instead.

The field lastError doesn't store the last error that occurred, but the error for the last attempt to notify (if any). This could be confusing because if a notification fails to deliver once but succeeds afterwards, this field will be empty. The name has been changed to lastAttemptError to better reflect this behavior.

[yuri-tceretian]

Suggested change

	lastAttemptDuration:
	lastAttemptDuration:
	description: duration of the last attempt to use the integration in humanized format, e.g. `1s` or `15ms`

[santihernandezc]

@yuri-tceretian I just added descriptions for the fields and generated the files.

[gotjosh]

While we don't necessarily need to stick 1:1 with Prometheus, it'd be good if similar things keep similar names. In prometheus, lastError https://github.com/prometheus/prometheus/blob/main/web/api/v1/api.go#L815-L818 is used for targets and conveys the same meaning as "last attempt".

Personally, I'd love to stick with lastError et al and a more clear description of the field that anyone can see in the API Spec but can see the argument for a more verbose approach. I'll leave it up to you ya'll, but wanted to provide some context.

[yuri-tceretian]

LGTM