Update Symfony server docs to be more highlighted

[Pierstoval]

I found the Docker-based setup very useful, and it was not really obvious to me that service names needed to be specific in order for the CLI to change the associated env vars.

That's why I thought adding a note tag to it would highlight it a bit more in order for it to be clear. Especially because this note shows the list of service names that are mandatory for Symfony CLI to adapt.

WDYT?

[fabpot]

We are always setting env vars. So, if your MySQL container is named db, env vars will be prefixed with DB_. The only specificity of naming it DATABASE_ is that Symfony Flex uses that by default. But having the possibility to choose the prefix is important when using more than 1 container of the same type.

[Pierstoval]

Well, this is not really the behavior I expected 😄 It's even better 😃

Would you suggest I add another line with the db service using the DB_URL env var, as a mark of example?

It could be more interesting to have more details about the exact checks that are done.

I would guess that it only changes the host+port part in the URL/DSN, but is this even close to truth? Could you give more specific details about the internals of these automated checks so the docs can be more self-explanatory using better examples that fit all cases? 🙂

[javiereguiluz]

@tucksaun could you please review this proposal to see if we can merge it or requires some changes? Thanks!

[tucksaun]

I have the feeling what we need instead is a small tweak of the section following this one (ie If your ``docker-compose.yaml`` file doesn't use the environment variable names...): we talk about variables names whereas we want to mention service names?

[javiereguiluz]

This contribution stalled ... should we close? Change anything? merge "as is"? Thanks.

[javiereguiluz]

Let's close this one and we can reconsider if we receive more feedback. Thanks.

[fabpot]

see #12391