Container Support

During sync we query list of tags present in the repo.

Pagination support is available for Tags API, we need update our sync code to cope with this change.
We'd need to check the `Link` header if it is present in the response headers.
For more docs check [0]
For Pulp2 implementation check [1]

1st request:
$ curl -i https://quay.io/v2/coreos/etcd/tags/list
HTTP/2 200 
server: nginx/1.14.0
date: Fri, 31 Aug 2018 13:13:56 GMT
content-type: application/json
content-length: 602
link: </v2/coreos/etcd/tags/list?next_page=gAAAAABbiT8UvBiyJvd3H5d7FS3azkmxqQuknl_2kKlKkbLpj_vGL_xv26HMBevZIVKY67vwpbKUo_Zact9vC6mjFd9KHGFGpkUHGc2jqGtd5aWpGbaIfqA%3D&n=50>; rel="next"
x-frame-options: DENY
strict-transport-security: max-age=63072000; preload

{"name":"coreos/etcd","tags":["v0.4.6","v0.5.0_alpha.0","v0.5.0_alpha.1","v0.5.0_alpha.2","v0.5.0_alpha.3","test","v0.5.0_alpha.4","v0.5.0_alpha.5","v2.0.0_rc.1","v2.0.0","v2.0.3","v2.0.4","v2.0.5","v0.4.8","v2.0.6","v2.0.7","v2.0.8","v2.0.9","v2.0.10","v2.1.0-alpha.0","v2.0.11","v2.0.12","v2.1.0-alpha.1","v2.0.13","v2.1.0-rc.0","v2.1.1","v2.2.0-alpha.0","v2.2.0-alpha.1","v2.1.2","v2.2.0-rc.0","v2.1.3","v2.2.0","v2.2.1","v2.3.0-alpha.0","v2.2.2","v2.2.3","v2.2.4","v2.2.5","v2.3.0-alpha.1","v2.3.0","v2.3.1","v2.3.2","v2.3.3","v3.0.0-beta.0","v2.3.4","v2.3.5","v2.3.6","v2.3.7","v3.0.0","v3.0.1"]}

2. check if Link is present. Then follow it until the Link disappears from the headers

$ curl -i 'https://quay.io/v2/coreos/etcd/tags/list?next_page=gAAAAABbiT8UvBiyJvd3H5d7FS3azkmxqQuknl_2kKlKkbLpj_vGL_xv26HMBevZIVKY67vwpbKUo_Zact9vC6mjFd9KHGFGpkUHGc2jqGtd5aWpGbaIfqA%3D&n=50'
HTTP/2 200 
server: nginx/1.14.0
date: Fri, 31 Aug 2018 13:15:36 GMT
content-type: application/json
content-length: 623
link: </v2/coreos/etcd/tags/list?next_page=gAAAAABbiT94xBPZc4VUD9_hx1bmHtfl1Xduxm811b1m06WiwW2mOHErnpkbtZ7Ag7ehYVPVAf3LfS2s-FVSrkCXhUqNLoduaGJaBorCUzp7NPlybCickC8%3D&n=50>; rel="next"
x-frame-options: DENY
strict-transport-security: max-age=63072000; preload

{"name":"coreos/etcd","tags":["v3.0.2","v3.0.3","v3.0.4","v3.0.5","v3.0.6","v3.0.7","v3.0.8","v3.0.9","v3.1.0-alpha.0","v3.0.10","v3.1.0-alpha.1","v3.0.11","v3.0.12","v3.1.0-rc.0","v3.0.13","v3.0.14","v3.0.15","v3.1.0-rc.1","v3.0.16","v3.0.17","v3.1.0","v2.3.8","v3.1.1","v3.1.2","v3.1.3","v3.1.4","v3.1.5","v3.1.6","v3.1.7","v3.2.0-rc.0","v3.2.0-rc.0-arm64","v3.2.0-rc.0-ppc64le","v3.1.8","v3.2.0-rc.1","v3.2.0-rc.1-arm64","v3.2.0-rc.1-ppc64le","v3.1.9","v3.2.0","v3.2.0-ppc64le","v3.2.1","v3.2.1-arm64","v3.2.1-ppc64le","v3.2.2","v3.2.2-arm64","v3.2.2-ppc64le","v3.0","v3.1.10","v3.2.3","v3.2.3-arm64","v3.2.3-ppc64le"]}

NOTE if registry does not support pagination, the Link header will be absent.
[0] https://docs.docker.com/registry/spec/api/#listing-image-tags
[1] https://github.com/pulp/pulp_docker/pull/262