Add warning regarding "/" in CS2_SERVERNAME

[Peeetman]

Using a "/" character in the CS2_SERVERNAME (e.g., "CS Server 1/3 of My Amazing LAN Party") causes the sed substitution in
https://github.com/joedwards32/CS2/blob/38b2938f7927c5f83e62fe32fe23f37e1f2201cb/bookworm/etc/entry.sh#L103to fail because the default delimiter "/" conflicts with the character in the value. Although the server continues to run, the configuration file ends up with unresolved placeholders (for example, {{SERVER_CHEATS}} remains unchanged). As a result, when players try to connect, they receive a "wrong password" error - even if the password is correct or none was set initially.

How to Reproduce:

1. take the example docker-compose.yml https://github.com/joedwards32/CS2/blob/38b2938f7927c5f83e62fe32fe23f37e1f2201cb/examples/docker-compose.yml
2. change the CS2_SERVERNAME to "Server 1/3"
3. docker compose up
4. connect to server
5. wrong password :(

Recommendation:
It is a lot of work to allow all sorts of arbitrary characters. I suggest just adding a warning in both the README and the example docker-compose.yml. I could provide another solution if requested.

Thank you for this amazing docker image and all of your work. It has been serving me and my friends well on our LAN parties <3 This is my first pull request ever created, so I hope the format and description are acceptable.

[joedwards32]

Thanks for the contribution!

I think you can use "/" if you escape them first, e.g. "\/".

[joedwards32]

Also, as "/" is being used as the delimiter in all sed substitutions I think it will cause problems for lots of other variables: https://github.com/joedwards32/CS2/blob/main/bookworm/etc/entry.sh#L103

[Peeetman]

It is technically possible to escape forward slashes / in all environment variables by applying an additional sed command, such as
echo "Server 1/3" | sed 's/\//\\\//g' # results in: Server 1\/3

However, this introduces actually the same issue: users must not use already escaped slashes \/ in their variables, as these will be double-escaped and may lead to unexpected behavior. While it may seem unlikely that someone would intentionally use \/ in a server name, that’s beside the point - the problem remains, and the sed substitution will silently fail or result in incorrect output without any feedback.

Proposed solution:
Warn users that if they really want to use a slash / in any Counter-Strike-related environment variable (e.g., in docker-compose.yml), it must be escaped by prepending a backslash \, as is standard in many configuration formats.

As you already noted, if users really want a slash to appear in their server name, they must escape it manually.
CS2_SERVERNAME="My Amazing Server 1\/3" # results in: My Amazing Server 1/3

I applied this to the current pull request.

[joedwards32]

I agree that documenting the requirement is better than trying to auto-escape / characters found in environment variables, getting that right is fiddly.

Maybe one day I will convert this all to python and jinja templates.

Approved. Thank you for your contribution.