Make an easy way to populate environment variables in the web container

[rfay]

What happened (or feature request):

TYPO3 users often request a way to set environment variables in the web container.

This is not hard to do with docker-compose.yaml, but we're really on course to take complete control of that file and recreate it on every start.

So we should provide a way to do it in config.yaml.

What you expected to happen:

How to reproduce this:

Version: Please include the output of ddev version, docker version and the project's .ddev/config.yaml.

Anything else do we need to know:

Related source links or issues:

Please use a complexity rating of 1-5 (5 is high) for a feature request. (High complexity implies more PR planning)

[kaystrobach]

suggestion:

beside the normal nginx-site.conf there should be an nginx-env-vars.conf

This file should have the same structure as /etc/nginx/fastcgi_params and could make it easy to add env vars ...

[rfay]

Nice work on this in #758 - it probably can't go in there because it's not general enough (TYPO3-oriented) but it certainly explains one way to do it.

[kaystrobach]

not typo3 specific ... the composer package is just env vars ... and uses composer plugin architecture

[rfay]

When reworking our setup of docker-compose.yml in #762 we can move away from using environment variables at all, and that will allow us to build a docker-compose.yml that populates the environment section more effectively.

[rfay]

Don't forget #758 when working on this, it's an important specific approach.

[rfay]

Added a writeup in https://stackoverflow.com/questions/50109020/how-can-i-set-environment-variables-inside-ddevs-containers