Allow cassandra-trunk docker image to be built from any repo/branch

[yukim]

Fixes #304

Added two build args:

• REPO
• BRANCH

to allow cassandra-trunk docker image to be built from any repo/branch.
For example, I used this change to build image from cep-15-accord branch to test Accord on kubernetes using cass-operator:

docker build -t ghcr.io/yukim/cass-management-api:cep-15-accord --build-arg="BRANCH=cep-15-accord" --file cassandra-trunk/Dockerfile.ubi8 --target cass-trunk --platform linux/amd64 .

[emerkle826]

So this will work as long as the branch you pick is based on a 5.0 version of Cassandra, and not a Release branch (i.e. the build artifact will be 5.0-SNAPSHOT). If not, then you will need to handle:

1. https://github.com/yukim/management-api-for-apache-cassandra/blob/feature/cassandra-repo-arg/cassandra-trunk/Dockerfile.ubi8#L53

As the build artifact is assumed to be 5.0-SNAPSHOT

2. https://github.com/yukim/management-api-for-apache-cassandra/blob/feature/cassandra-repo-arg/cassandra-trunk/Dockerfile.ubi8#L90-L97

You also have to adjust which artifacts of Management API are removed, kept and sym-linked in the section above. There are different artifacts built for different versions of Cassandra and things won't work if you include the wrong one.

3. https://github.com/yukim/management-api-for-apache-cassandra/blob/feature/cassandra-repo-arg/cassandra-trunk/Dockerfile.ubi8#L103

The CDC_AGENT_EDITION variable also needs to changed, depending on which version of Cassandra.

Having said all this, your changes should work as long as the branch is a 5.0-SNAPSHOT version. Seeing as how this Dockerfile is in the cassandra-trunk folder, I think that is a safe assumption for now.

I can approve this PR as-is, with all of the above caveats noted. However, it would be nice if you could figure out a way to deduce the Cassandra version so it's not hardcoded to 5.0-SNAPSHOT here: https://github.com/yukim/management-api-for-apache-cassandra/blob/feature/cassandra-repo-arg/cassandra-trunk/Dockerfile.ubi8#L53

Let me know if you are willing to try this and I can wait to approve this PR then. If not, I think I can approve it now and this can be addressed later.