close #8903

In #8903 we observed JSON
decoding error to have the following error message in the log:

```
Error processing HTTP request: Resource temporarily unavailable: 3956 (pageserver-6.ap-southeast-1.aws.neon.tech) error receiving body: error decoding response body
```

This is hard to understand. In this patch, we make the error message
more reasonable.

## Summary of changes

* receive body error is now an internal server error, passthrough the
`reqwest::Error` (only decoding error) as `anyhow::Error`.
* instead of formatting the error using `to_string`, we use the
alternative `anyhow::Error` formatting, so that it prints out the cause
of the error (i.e., what exactly cannot serde decode).

I would expect seeing something like `error receiving body: error
decoding response body: XXX field not found` after this patch, though I
didn't set up a testing environment to observe the exact behavior.

---------

Signed-off-by: Alex Chi Z <[email protected]>

close #8903

In #8903 we observed JSON
decoding error to have the following error message in the log:

```
Error processing HTTP request: Resource temporarily unavailable: 3956 (pageserver-6.ap-southeast-1.aws.neon.tech) error receiving body: error decoding response body
```

This is hard to understand. In this patch, we make the error message
more reasonable.

## Summary of changes

* receive body error is now an internal server error, passthrough the
`reqwest::Error` (only decoding error) as `anyhow::Error`.
* instead of formatting the error using `to_string`, we use the
alternative `anyhow::Error` formatting, so that it prints out the cause
of the error (i.e., what exactly cannot serde decode).

I would expect seeing something like `error receiving body: error
decoding response body: XXX field not found` after this patch, though I
didn't set up a testing environment to observe the exact behavior.

---------

Signed-off-by: Alex Chi Z <[email protected]>