gitlabnet.go

In future, we'll need to perform http requests for Geo related
code area.

We cannot use retryable requests because:

- It's not necessary for the to be retryable
- In order to retry, the whole request body is stored in RAM,
while we need to stream large blobs of data

This commit:

- Extracts logging into a separate round tripper in order to
reuse it for other http requests by default
- Defines Do function that accepts raw request as an argument