factor out image serving

[pweil-]

Abstract out the impl of serving images which will allow us to inject different types of server (useful for mocking in test if nothing else).

@simon3z @enoodle

I did notice the content url has / on it so you have to curl http://0.0.0.0:8080/api/v1/content/ vs http://0.0.0.0:8080/api/v1/content to get the content. If you curl just http://0.0.0.0:8080/api/v1/content you'll get Permanently Moved.

Testing:

[pweil@localhost openshift-docs]$ curl 0.0.0.0:8080/healthz
ok
[pweil@localhost openshift-docs]$ curl 0.0.0.0:8080/api
{
  "versions": [
    "v1"
  ]
}
[pweil@localhost openshift-docs]$ curl 0.0.0.0:8080/api/v1/metadata
{
  "Id": "sha256:8b5cf972e254795d1eef4f66e1a71d3c6869bbf4773d9fb36fd8c13ead1a9d5d",
  "Created": "2016-02-18T16:47:39.452282864Z",
  "Container": "f8fb8c4a27ffec2f7fa19595696c7c42754cf6a80b309d56f014090a5f4bc54a",
  "ContainerConfig": {
    "Hostname": "f8fb8c4a27ff",
    "Cmd": [
      "/bin/sh",
      "-c",
      "#(nop) ADD file:b472211c9fa1cd451ea7e94eee2ef1cdaae0413110f560bce5cb183a795b47d7 in /"
    ],
    "Image": "b0082ba983ef3569aad347f923a9cec8ea764c239179081a1e2c47709788dc44",
    "Entrypoint": null
  },
  "DockerVersion": "1.9.1",
  "Author": "Adam Miller \u003cmaxamillion@fedoraproject.org\u003e",
  "Config": {
    "Hostname": "f8fb8c4a27ff",
    "Cmd": null,
    "Image": "b0082ba983ef3569aad347f923a9cec8ea764c239179081a1e2c47709788dc44",
    "Entrypoint": null
  },
  "Architecture": "amd64",
  "Size": 188718134,
  "VirtualSize": 188718134
}
[pweil@localhost openshift-docs]$ curl 0.0.0.0:8080/api/v1/content/
curl: (18) transfer closed with 9223372036854775807 bytes remaining to read

[pweil-]

actually, this won't work here, need to set it later since we manipulate the DstPath later for tmpfs if it's empty. Will fix up

[simon3z]

@pweil- I need to queue this behind #3

[pweil-]

no worries, I'll rebase as necessary

[enoodle]

why do you call this file webdav.go and not imageserver.go? not everything here is served with webdav.

[pweil-]

I'll rename.

[enoodle]

@pweil- @simon3z we should have this on openshift/image-inspector. it would help alot there, especially with the new commits we need better structure.

[simon3z]

@enoodle please do