Update and consolidate Docker Compose variable documentation.

[bozau]

Hi,

I've consolidated variable substitution documentation for Docker Compose into a single location as recommended by @ShadowArcanist, previously there were three separate locations, these were;

https://coolify.io/docs/knowledge-base/environment-variables#shared-variables
https://coolify.io/docs/knowledge-base/docker/compose#defining-environment-variables
https://coolify.io/docs/builds/packs/docker-compose#defining-environment-variables

I also added additional information regarding shared variables and how to configure and consume them better.

I hope that this will better help people on-boarding with Docker Compose.

Cheers.

Aaron.

[github-actions]

Hi @bozau,

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[Cinzya]

We recommend defining environment variables using upper snake case, we should keep that consinstent through out the docs. Maybe also give it a more generic name, which aligns better with the other examples.

Suggested change

	- SOME_OPTIONAL_VARIABLE=${EnvironmentNameShort} # Creates an editable, uninitialized variable in the UI.
	- SOME_OPTIONAL_VARIABLE=${SOME_VARIABLE_IN_COOLIFY_UI} # Creates an editable, uninitialized variable in the UI.

[Cinzya]

I believe this can be a bit confusing for people. Thinking that the application env and the shared env need to share the same name, which afaik is not the case. Maybe we can re-name them, to mak the difference clear what is what.

Suggested change

	EnvironmentNameShort={{environment.EnvironmentNameShort}}
	SOME_VARIABLE_IN_COOLIFY_UI={{environment.SOME_SHARED_VARIABLE}}

[Cinzya]

as already mentioned above.

Suggested change

	Or in the normal view, the Name is what's referenced in the Docker Compose file `EnvironmentNameShort` with the Value being the referenced environment variable `{{environment.EnvironmentNameShort}}` as seen below. Once saved if correct, you'll see there's a third text box, if you reveal this, you should be able to see the true value.
	Or in the normal view, the Name is what's referenced in the Docker Compose file `SOME_VARIABLE_IN_COOLIFY_UI` with the Value being the referenced environment variable `{{environment.SOME_SHARED_VARIABLE}}` as seen below. Once saved if correct, you'll see there's a third text box, if you reveal this, you should be able to see the true value.

[Cinzya]

I think it would actually be better, to move everything in here, instead of /builds/packs/docker-compose#shared-environment-variables. Makes semantically more sense to have everything environment variables related under the environment variables page.
The Build Pack Docker Compose page is already long enough by itself.

[bozau]

Sure can do if that's the preferred location :)

[Cinzya]

shouldn't this + the magic environment section be moved as well then? They work the same across both as well.

[bozau]

I'll check it out, I haven't personally used any of the magic variables in my docker compose, but I suspect you'll be correct.
From what I understand, the magic variables are across all of Coolify, and not docker compose specific right? If so, they probably should sit in the Environment Variables page, yeah?

[Cinzya]

They are actually Docker Compose specific, so I would say we add them in the Environment Variables page under Docker Compose.
Appreciate the work btw! 😊

[bozau]

Hi @Cinzya and @ShadowArcanist ,

I believe that I've completed the changes including the suggestions, could you double check I've not missed something :)

Cheers.