Match Error on Filtering indexed String columns

[osopardo1]

What went wrong?
When doing a query on a string indexed column, the Spark type UTF8String is not recognized by the Transformation method and it throws a Match error.

This is the result of filtering the e-commerce dataset indexed with qbeast by "brand == 'versace'"

versace (of class org.apache.spark.unsafe.types.UTF8String)
scala.MatchError: versace (of class org.apache.spark.unsafe.types.UTF8String)
	at io.qbeast.core.transform.HashTransformation.transform(HashTransformation.scala:11)
	at io.qbeast.core.model.QuerySpaceFromTo$.$anonfun$apply$1(QuerySpace.scala:68)
	at scala.collection.immutable.List.map(List.scala:293)
	at io.qbeast.core.model.QuerySpaceFromTo$.apply(QuerySpace.scala:67)
	at io.qbeast.spark.index.query.QuerySpecBuilder.extractQuerySpace(QuerySpecBuilder.scala:107)
	at io.qbeast.spark.index.query.QuerySpecBuilder.build(QuerySpecBuilder.scala:144)
	at io.qbeast.spark.index.query.QueryExecutor.$anonfun$execute$1(QueryExecutor.scala:22)

The solution is to detect the spark type before calling core functions and parse it to the string representation.

How to reproduce?

1. Code that triggered the bug, or steps to reproduce:

   val tmpDir = "/tmp/qbeast"

    val data = spark.read
    .format("csv")
    .option("header", "true")
    .option("inferSchema", "true")
    .load("src/test/resources/ecommerce100K_2019_Oct.csv")
    .distinct().na.drop()

   data.write
      .mode("overwrite")
      .format("qbeast")
      .options(
        Map("columnsToIndex" -> "brand,product_id", "cubeSize" -> "10000"))
      .save(tmpDir)

  val indexed = spark.read.format("qbeast").load(tmpDir)
  indexed.filter("brand == 'versace'").show()

2. Branch and commit id:

main on c182980
3. Spark version:
On the spark shell run spark.version.

3.1.2

4. Hadoop version:
   On the spark shell run org.apache.hadoop.util.VersionInfo.getVersion().

3.2.0

5. Are you running Spark inside a container? Are you launching the app on a remote K8s cluster? Or are you just running the tests in a local computer?

On local computer

6. Stack trace:

[eavilaes]

Closing per #59