feat: allow configuration of composer version in integration tests

[kolaente]

This PR provides a way to configure the composer version used in integration tests.

Composer 2 was only installed in the Dockerfile for 7.4 so I added the config option only there. IIRC composer 2 requires 7.4? (or at least 7.3?)

[fooman]

@kolaente this looks good to me but just to confirm that I read it right, this would not break any existing scripts that use composer without version suffix as we symlink the 1 version on start up?

[damienwebdev]

This needs to be shared across to PHPStan as well since they use the same version under the hood.

[kolaente]

@fooman Yes, it should break any existing scripts.

[kolaente]

@damienwebdev That's probably the time when we should put the effort in to create a base image that lets you switch between versions. See #25 (comment)

[sprankhub]

Very good change! Thanks @kolaente! However, given that Composer 1 is really EOL, I suggest switching the default to version 2 even if this is a breaking change in some cases.

[jissereitsma]

Sorry for the long delay. Just to reiterate the statement of @kolaente - he mentioned that it "should break" but I think that was a typo so I interpret it as "should not break". Looking at the change, I think this is safe to adopt. If it break, let's fix it. If it works, let's implement it elsewhere.

[kolaente]

he mentioned that it "should break" but I think that was a typo so I interpret it as "should not break".

oh yes, that's definitely a typo.