Collect global Envvars

[kobergj]

Compose a list of envvars living in more than 1 service

[mmattel]

We need to change in the adoc template file two things:

• [width="100%",cols="30%,20%,~,~,~",options="header"]
  the first two columns need a fixed width
• for the xref column only, a| [subs=attributes+]
-attributes --> attributes+

Then, as you can see, we need, if possible two sortings 🙈

• all services listed should be sorted alphabetical ascending
  see in the image above that the app-provider service is "somewhere" in the middle and therefore hard to identify. the list is usually looong.
• if possible, the names of the envvars should be sorted ascending

[kobergj]

@mmattel yes good point 👍 I was not 100% sure what you mean by

if possible, the names of the envvars should be sorted ascending

so I sorted them alphabetically. Should I sort by number of services?
Rest is implemented as requested.

[mmattel]

I'll check the result of the last change, build is running

[mmattel]

LGTM, a build and check on staging looks perfect 😄 👍

[mmattel]

When merged, I will backport the global adoc file to the stable docs branch.