exporter-collector-http: log error when it fails to export

[vmarchaud]

Currently the collector-exporter in HTTP just log that the export failed with only the status code. We should get the error and log it in the console for end users to find what's wrong.
For example i was debugging an 400 and to debug i had to publish another package with more logs to see that the error was:

{"error":"Request was missing field timeSeries[0].points[0].interval.endTime: The end time of the interval is required.","code":3,"message":"Request was missing field timeSeries[0].points[0].interval.endTime: The end time of the interval is required."}

cc @obecny do you want to tackle it ?

[obecny]

@vmarchaud sure

[obecny]

@vmarchaud I think this will be irrelevant once the global error handler is implemented -> #1415

[vmarchaud]

Well on the error handling side yes, one thing we could add on the error still is the response body.

[vmarchaud]

I needed that for my deployment so i've developped it, hope you didn't started that in the mean time

[dyladan]

@vmarchaud does #1607 fix this issue? If so, please link the PR.

[vmarchaud]

@dyladan Done, i though it was autoamtic if i tagged the issue in the PR title :/