Merge pull request #274 from tobiasge/optimise-builds ...

Optimise builds

Dockerfile: Fixed file permissions for media

Add checks to verifiy if a new build is needed ...

This checks if the source materials (python image, Netbox commit,
netbox-docker commit) have changed since the last build. This check is done
by comparing the digest and commit ids from the previous image with the
given tag to the current values taken from the Git and Docker repositories.

The checks are only performed for builds by the automated builds on Github.

Prepare for Netbox 2.7

Merge pull request #186 from netbox-community/non-root ...

Non root

Revert "Fix #179 'libc not found'" ...

This reverts commit feb810a.

Remove the named user, change permissions to 'g+w'

Adds netbox user

Adds more labels to the Dockerfile ...

It also updates the README and the bug_report template to reflect
the changes. Additionally, in the README some relevant shields from
shields.io are added.

The labels follow [label-schema.org][lsorg] and the [OpenContainer
image spec, section annotations][ocis], specifications.

[lsorg]: http://label-schema.org/rc1/
[ocis]: https://github.com/opencontainers/image-spec/blob/master/annotations.md

Fix #179 'libc not found' ...

Gunicorn version 20 crashes in this docker image. So for now use a
version <20.

Optimize pip install command ...

As mentioned by @sdktr the "--install-option" is redundant. The added
"--no-warn-script-location" is used to silence warnings when installing
into a directory that is not on $PATH.

Fixes #170 - "drf-yasg" installed into wrong dir ...

With the new multistage build the pip install command put some packages
in the wrong directory. This resuled in them not being copied into the
runtime images. This commit add the additional "--prefix" option to the
install command. After that all test run and we no longer get the error
"ModuleNotFoundError: No module named 'drf_yasg'".

Remove trailing space in Dockerfile

Checkout the repository with git ...

This changes the build process even further. Instead
f using `wget` to fetch the current code, `git` is used.
This allows for faster switching between branches,
because only the differences between them have to be
fetched from the server.

But the main advantage is that the build cache can
finally be used as designed by Docker. Repetitive
builds are very fast now. This is also true between
branches and tags, as long as the `requirements.txt`
file doesn't change.

externalize netbox download with wget

Refactor to multistage builds ...

This commit introduces a huge change in the build process.

What changed:

- Dockerfile.ldap was integrated into Dockerfile as a seperate
  [build stage][multistage-build].
- All the build scripts were refactored according to this.
- The `docker-compose.yml` file was adjusted likewise.
- The main build script, `/build.sh`, now always builds all
  targets (formerly called variants).
- The minimal requirements for Docker and docker-compose
  have increased.
- The build on hub.docker.com must be adjusted.

This change should also fix #156 permanently.

[multistage-build]: https://docs.docker.com/develop/develop-images/multistage-build/

fix AttributeError for ruamel.yaml

Update base image ...

This updates the base image to Alpine 3.10 with Python 3.7

%s/digitalocean/netbox-community/gi ...

Thank you Digitalocean for sponsoring Netbox!
And thank you for letting it grow up and move out ;)

Explain caching strategy in Dockerfile comments

Changing REF_URL to use HEAD/TAG agnostic API ...

Per [dicsuccion](https://github.com/netbox-community/netbox-docker/pull/137#issuecomment-495667921) with @cimnine, changing the API endpoint to one that retains functionality of previous URL while supporting both HEADS and TAGS

Adding REF to GitHub repo HEAD for cache busting ...

After installing requirements, check if  HEAD has changed and bust cache for RUN instruction for wget  archive

Caching of requirements.txt ...

After [a discussion][1] with rje6459 on the networktocode Slack
in the #netbox-docker channel we've come up with a small improvement
to those that regularly have to build netbox docker locally.

It fetches the "requirements.txt" from the desired branch before
downloading netbox itself.

[1]: https://networktocode.slack.com/archives/CD23LP8BC/p1558537080023200

Update django to 2.2

Loosen version pinning for Django ...

This change is in accordance with https://github.com/digitalocean/netbox/issues/2808

Update Alpine ...

This updates to the newest stable version (Alpine 3.9)

Update Alpine ...

This updates to the newest stable version (Alpine 3.8)

✨ Don't lock Django to explicit version ...

... but rather use the same definition that is currently used in
Netbox's `requirements.txt`.

♻️ Make netbox-worker it's own container ...

One container should ideally have one responsibility [1]. Therefore I
implemented the netbox-worker to start in it's own container. This is
possible, because netbox and the worker communicate via redis anyway.

They still use the same image underneath, just the "command" they
execute while starting different.

Or in other words: I see no reason to introduce supervisord, when we
already have docker-compose which can take care of running multiple
processes.

Also, here's another benefit: Now it's possible to view the logs of the
webhook worker independently of the other netbox logs (and vice-versa).

Other changes in this commit:
* I don't see a reason to put a password for Redis in the docker-compose
  setup, so I removed it.
* Slightly changed the nginx config, so that the nginx startup command
  becomes simpler and any error should be visible in the docker log.
* Some housekeeping in the `Dockerfile`.
* Added some troubleshooting advice regarding webhooks to the README.

I'd like to thank Brady (@bdlamprecht [2]) here who did the harder
work of figuring out what's even required to have webhooks working. [3]

[1] 
https://docs.docker.com/develop/develop-images/dockerfile_best-practices/#decouple-applications
[2] https://github.com/bdlamprecht
[3] https://github.com/ninech/netbox-docker/pull/90

Working implementation of webhooks using new 'redis' container