Prepare for Netbox 2.7

Building the Docker image with Github Actions

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

Non root

Merge pull request #195 from netbox-community/update-postgres ...

Update PostgreSQL to 11

Better safe than sorry, keep PostgreSQL at 11 for now.

update postgres to 12

update redis

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

Adds netbox user

Update docker-compose.yml

Update Nginx 1.17.6-alpine docker-compose.yml

Merge branch 'custom-scripts' of https://github.com/ScanPlusGmbH/netbox-docker into ScanPlusGmbH-custom-scripts

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/

Add support for custom scripts ...

Custom scripts were added to Netbox in version 2.6.3. This adds a new
directory to the image where custom scripts can be placed.

Add shared (z) container volume SELinux labels to the volumes created by docker-compose.

Update references to netboxcommunity

Changing 'reports' from a volume to a mapped directory ...

This will allow eaiser interaction with the report functionality of the 'netbox' container.

Moving env files into separate directory for better organization

🆙 Update nginx to the latest version

✨ Use a default Redis password ...

Although it does not provide any additional security, it shows how to
configure Redis with a password and how to use Netbox using a password
protected redis server. Something that might be considered in a classic
production deployment. (But is mostly irrelevant in e.g. a Kubernetes /
OpenShift deployment as the isolation is usually on a network level.)

♻️ 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

✨docker-compose: use latest postgres minor version (10.4)

Move config to /etc/netbox/config (Fixes #54) ...

With this the configuration is moved to /etc/netbox/config and the
default reports directory is set to /etc/netbox/reports. This enables
the user to mount reports from a config map or persistent volume in
OpenShift.

Modifications for Openshift ...

With these modifications the netbox containers can run on Openshift.
The configuration files can be imported from a config map to the
'/etc/netbox' directory and will be loaded from there.

⬆️ Updates Dependencies ...

* Postgres 9.6 -> 10.2
* Nginx 1.11 -> 1.13

❇️ Make relevant mounts read-only ...

Some mounts are not supposed to be writable by
a container. The docker-compose file has been
improved in that direction in order to enforce this.

✨ Include Initializers ...

Initializers are startup scripts for common tasks like creating custom
fields. These are problems many users of Netbox Docker potentially face
and are therefore worth sharing.

Load custom fields when creating the container.