Really Adding detection for transient generation of invalid json in ChangeFeedStartFromInternal (Azure#20996)

* Really Adding detection for transient generation of invalid json in ChangeFeedStartFromInternal

* Fixing StackOverflow error due to unintentional recursion

* Addressing test flakiness

Author: FabianMeiswinkel

sdk/cosmos/azure-cosmos-spark_3-1_2-12/src/test/scala/com/azure/cosmos/spark/PartitionMetadataCacheITest.scala

@@ -96,7 +96,7 @@ class PartitionMetadataCacheITest
       newStaleCachedItemRefreshPeriodInMsOverride = Some(10 * 1000),
       newCachedItemTtlInMsOverride = Some(50))
 
-    Thread.sleep(500)
+    Thread.sleep(2000)
     //scalastyle:on magic.number
 
     PartitionMetadataCache.purge(containerConfig, feedRange) shouldEqual false

sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/changefeed/implementation/ChangeFeedStartFromInternal.java

@@ -43,12 +43,17 @@ public void populatePropertyBag() {
     }
 
     @Override
-    public String toString()
-    {
-        String json = this.toJson();
+    public String toString() {
+        return this.toJson();
+    }
+
+    @Override
+    public String toJson() {
+        String json = super.toJson();
 
         if (json.indexOf("\"Type\":") != json.lastIndexOf("\"Type\":")) {
             // TODO @fabianm Remove as soon as root caused - https://github.com/Azure/azure-sdk-for-java/issues/20635
+            // "StartFrom":{"Type":"NOW","Type":"NOW"}
             throw new IllegalStateException("There shouldn't be any duplicate json properties!");
         }