#184 Add the method to the Source trait that should make performance …

…optimization possible in the future.

pramen/api/src/main/scala/za/co/absa/pramen/api/Source.scala

@@ -26,6 +26,14 @@ import java.time.LocalDate
   * Transfer jobs are used to read data from a source and write it to a sink.
   */
 trait Source extends ExternalChannel {
+  /**
+    * If true, getRecordCount() won't be used to determine if the data is available.
+    * This saves performance ond double data read for
+    *  - File sources when input files are always available (lookup tables for instance)
+    *  - Snapshot-based sources.
+    */
+  def isDataAlwaysAvailable: Boolean = false
+
   /**
     * Returns the record count based on the particular input period and query.
     */