additional log verbosity for Prometheus receiver

[tomklino]

Component(s)

Prometheus receiver

Is your feature request related to a problem? Please describe.

I'm getting multiple log reading "unable to scrape target" with the only details provided to me is the target experiencing the issue. There is no information hinting for the cause.

Describe the solution you'd like

A helpful log message describing the cause.
For example:

• timeout
• unauthorized
• empty reply

In addition, it would also be helpful if the log message would include possible hints for a solution, such as:

• inspect the service monitor resource named ABC
• inspect the configuration file for the OpenTelemetry collector

Describe alternatives you've considered

I've looked in the code for the line writing this error message and unfortunately it's located somewhere that can't provide more info on the issue. It seems to me that at this point it already has the response and only inspecting it. To log the cause for the error would probably need to be done somewhere else

I've also found other issues opened in this repo, but their solutions were not relevant for me

Additional context

No response

[VihasMakwana]

I'll have a look and see if it can be improved.