[imporve] fix scalastyle issues

[nlu90]

(If this PR fixes a github issue, please add Fixes #<xyz>.)

Fixes #

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Motivation

mvn verify reported the following scala style issue:

error file=/home/runner/work/pulsar-spark/pulsar-spark/src/main/scala/org/apache/spark/sql/pulsar/CachedConsumer.scala message=There should at least one a single empty line separating groups java and scala. line=17 column=0
error file=/home/runner/work/pulsar-spark/pulsar-spark/src/main/scala/org/apache/spark/sql/pulsar/CachedConsumer.scala message=There should at least one a single empty line separating groups scala and 3rdParty. line=18 column=0
error file=/home/runner/work/pulsar-spark/pulsar-spark/src/main/scala/org/apache/spark/sql/pulsar/CachedConsumer.scala message=There should at least one a single empty line separating groups 3rdParty and spark. line=22 column=0
error file=/home/runner/work/pulsar-spark/pulsar-spark/src/main/scala/org/apache/spark/sql/pulsar/CachedPulsarClient.scala message=There should at least one a single empty line separating groups 3rdParty and spark. line=26 column=0
error file=/home/runner/work/pulsar-spark/pulsar-spark/src/main/scala/org/apache/spark/sql/pulsar/PulsarHelper.scala message=There should at least one a single empty line separating groups 3rdParty and spark. line=33 column=0
error file=/home/runner/work/pulsar-spark/pulsar-spark/src/main/scala/org/apache/spark/sql/pulsar/PulsarSinks.scala message=There should at least one a single empty line separating groups 3rdParty and spark. line=22 column=0
error file=/home/runner/work/pulsar-spark/pulsar-spark/src/main/scala/org/apache/spark/sql/pulsar/PulsarSinks.scala message=SparkSession should come before SQLContext. line=23 column=28
error file=/home/runner/work/pulsar-spark/pulsar-spark/src/main/scala/org/apache/spark/sql/pulsar/PulsarSourceRDD.scala message=File line length exceeds 100 characters line=102

Modifications

Describe the modifications you've done.

Verifying this change

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This change is a trivial rework / code cleanup without any test coverage.

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This change is already covered by existing tests, such as (please describe tests).

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This change added tests and can be verified as follows:

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• Added integration tests for end-to-end deployment with large payloads (10MB)
• Extended integration test for recovery after broker failure

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[tisonkun]

LGTM.

Although, I wonder if we have a CI workflow to guard this result. That is, we don't have such a CI workflow by GitHub Actions. I can see a Jenkins file but we don't require it in check state?

[nlu90]

@tisonkun Yes, we need such a workflow to do a scala-style check.

Currently, these errors are reported during the release process.

[nlu90]

#128 For future improvement