Add HeaderSizeError for downstream consumers to match on

When raising header size mismatches, use this specific error.

It will cause, for example, exception reporting software like Sentry to
correlate these exceptions separately from logical errors like a bad Decoder

csv/src/fs2/data/csv/exceptions.scala

@@ -20,3 +20,7 @@ class CsvException(msg: String, inner: Throwable = null) extends Exception(msg,
 class DecoderError(msg: String, inner: Throwable = null) extends CsvException(msg, inner)
 
 class HeaderError(msg: String, inner: Throwable = null) extends CsvException(msg, inner)
+
+/** Raised when processing a Csv row whose width doesn't match the width of the Csv header row */
+class HeaderSizeError(msg: String, val expectedColumns: Int, val actualColumns: Int, inner: Throwable = null)
+    extends HeaderError(msg, inner)

csv/src/fs2/data/csv/internals/CsvRowParser.scala

@@ -26,12 +26,14 @@ private[csv] object CsvRowParser {
   def pipe[F[_], Header](implicit F: RaiseThrowable[F],
                          Header: ParseableHeader[Header]): Pipe[F, NonEmptyList[String], CsvRow[Header]] =
     _.pull.uncons1.flatMap {
-      case Some((firstRow, tail)) =>
-        Header(firstRow) match {
+      case Some((currentRow, tail)) =>
+        Header(currentRow) match {
           case Left(error) => Pull.raiseError[F](error)
-          case Right(headers) if headers.length =!= firstRow.length =>
-            val error = new HeaderError(
-              s"Got ${headers.length} headers, but ${firstRow.length} columns. Both numbers must match!")
+          case Right(headers) if headers.length =!= currentRow.length =>
+            val error = new HeaderSizeError(
+              s"Got ${headers.length} headers, but ${currentRow.length} columns. Both numbers must match!",
+              expectedColumns = headers.length,
+              actualColumns = currentRow.length)
             Pull.raiseError[F](error)
           case Right(headers) =>
             tail