DBZ-8024: Fix bug with multiple transforms

[ryanvanhuuksloot]

When you apply multiple transformations, you run into a bug with the operator where the t0,t1 isn't applied like it should be. There is something wrong with String.join(","). Realistically we just need to add a comma between.

Also fixes the incorrect test so we can validate this better moving forward.

Real World Example

1 Transformation ✅

debezium.transforms.t0.negate=true
debezium.transforms.t0.predicate=TopicNameMatches
debezium.transforms.t0.topic.regex=<redacted>
debezium.transforms.t0.topic.replacement=<redacted>
debezium.transforms.t0.type=io.debezium.transforms.ByLogicalTableRouter
debezium.transforms=t0

When you have multiple transformations ❌

debezium.transforms.t0.negate=false
debezium.transforms.t0.predicate=TopicNameMatches
debezium.transforms.t0.type=<custom transform>
debezium.transforms.t1.negate=false
debezium.transforms.t1.predicate=TopicNameMatches
debezium.transforms.t1.regex=<redacted>
debezium.transforms.t1.replacement=<redacted
debezium.transforms.t1.type=org.apache.kafka.connect.transforms.RegexRouter
debezium.transforms.t2.negate=false
debezium.transforms.t2.predicate=TopicNameMatches
debezium.transforms.t2.type=<custom transform>
debezium.transforms.t3.negate=false
debezium.transforms.t3.predicate=TopicNameMatches
debezium.transforms.t3.type=<custom transform>
debezium.transforms=

Note the debezium.transforms is empty in the second example

[github-actions]

Hi @ryanvanhuuksloot, thanks for your contribution. Please prefix the commit message(s) with the DBZ-xxx JIRA issue key.

[ryanvanhuuksloot]

I don't have access to RH Jira yet so for now I'm leaving this with the incorrect DBZ branch structure

[jcechace]

@ryanvanhuuksloot LGTM, let me know if I should create the jira or whether you already managed to get an access. Once we can prefix the commit message I will merge it.

[ryanvanhuuksloot]

@jcechace Done! Thanks!