* fix hard-coded timeout and error panic in API archive download endpoint
This commit updates the `GET /api/v1/repos/{owner}/{repo}/archive/{archive}`
endpoint which prior to this PR had a couple of issues.
1. The endpoint had a hard-coded 20s timeout for the archiver to complete after
which a 500 (Internal Server Error) was returned to client. For a scripted
API client there was no clear way of telling that the operation timed out and
that it should retry.
2. Whenever the timeout _did occur_, the code used to panic. This was caused by
the API endpoint "delegating" to the same call path as the web, which uses a
slightly different way of reporting errors (HTML rather than JSON for
example).
More specifically, `api/v1/repo/file.go#GetArchive` just called through to
`web/repo/repo.go#Download`, which expects the `Context` to have a `Render`
field set, but which is `nil` for API calls. Hence, a `nil` pointer error.
The code addresses (1) by dropping the hard-coded timeout. Instead, any
timeout/cancelation on the incoming `Context` is used.
The code addresses (2) by updating the API endpoint to use a separate call path
for the API-triggered archive download. This avoids producing HTML-errors on
errors (it now produces JSON errors).
Signed-off-by: Peter Gardfjäll <peter.gardfjall.work@gmail.com>
