fix: change putDimensions to update latest key-value for duplicates

This change ensures new dimension key-values are used for the EMF root node
by moving duplicates to the end of the collection.

Example:

```
[
  { "keyA": "value1" },
  { "keyA": "value2" },
]

// expected target member: { "keyA": "value2" }
```

[TESTING]

Updated unit tests to check for this case wherein putDimensions
may be triggered using various dimension set lengths, values, and order.

Author: Aaron Michael Lamb

src/main/java/software/amazon/cloudwatchlogs/emf/model/MetricDirective.java

@@ -51,12 +51,16 @@ class MetricDirective {
         shouldUseDefaultDimension = true;
     }
 
+    /**
+     * Adds a dimension set to the end of the collection.
+     *
+     * @param dimensionSet
+     */
     void putDimensionSet(DimensionSet dimensionSet) {
-        if (dimensions.stream()
-                .anyMatch(dim -> dim.getDimensionKeys().equals(dimensionSet.getDimensionKeys()))) {
-            return;
-        }
-
+        // Duplicate dimensions sets are removed before being added to the end of the collection.
+        // This ensures only latest dimension value is used as a target member on the root EMF node.
+        // This operation is O(n^2), but acceptable given sets are capped at 10 dimensions
+        dimensions.removeIf(dim -> dim.getDimensionKeys().equals(dimensionSet.getDimensionKeys()));
         dimensions.add(dimensionSet);
     }
 

src/test/java/software/amazon/cloudwatchlogs/emf/model/MetricDirectiveTest.java

@@ -117,12 +117,14 @@ public void testPutMultipleDimensionSets() throws JsonProcessingException {
     @Test
     public void testPutMultipleDuplicateDimensionSets() throws JsonProcessingException {
         MetricDirective metricDirective = new MetricDirective();
+        metricDirective.putDimensionSet(new DimensionSet());
         metricDirective.putDimensionSet(DimensionSet.of("Region", "us-east-1"));
         metricDirective.putDimensionSet(
                 DimensionSet.of("Region", "us-east-1", "Instance", "inst-1"));
         metricDirective.putDimensionSet(
                 DimensionSet.of("Instance", "inst-1", "Region", "us-east-1"));
         metricDirective.putDimensionSet(DimensionSet.of("Instance", "inst-1"));
+        metricDirective.putDimensionSet(new DimensionSet());
         metricDirective.putDimensionSet(DimensionSet.of("Region", "us-east-1"));
         metricDirective.putDimensionSet(
                 DimensionSet.of("Region", "us-east-1", "Instance", "inst-1"));
@@ -134,7 +136,32 @@ public void testPutMultipleDuplicateDimensionSets() throws JsonProcessingExcepti
 
         assertEquals(
                 serializedMetricDirective,
-                "{\"Dimensions\":[[\"Region\"],[\"Region\",\"Instance\"],[\"Instance\"]],\"Metrics\":[],\"Namespace\":\"aws-embedded-metrics\"}");
+                "{\"Dimensions\":[[],[\"Region\"],[\"Instance\",\"Region\"],[\"Instance\"]],\"Metrics\":[],\"Namespace\":\"aws-embedded-metrics\"}");
+    }
+
+    @Test
+    public void testPutMultipleDimensionsWillOrderCorrectly() throws JsonProcessingException {
+        MetricDirective metricDirective = new MetricDirective();
+        metricDirective.putDimensionSet(new DimensionSet());
+        metricDirective.putDimensionSet(DimensionSet.of("Region", "us-east-1"));
+        metricDirective.putDimensionSet(
+                DimensionSet.of("Region", "us-east-1", "Instance", "inst-1"));
+        metricDirective.putDimensionSet(
+                DimensionSet.of("Instance", "inst-1", "Region", "us-east-1"));
+        metricDirective.putDimensionSet(DimensionSet.of("Instance", "inst-1"));
+        metricDirective.putDimensionSet(
+                DimensionSet.of("Region", "us-east-1", "Instance", "inst-1"));
+        metricDirective.putDimensionSet(
+                DimensionSet.of("Instance", "inst-1", "Region", "us-east-1"));
+        metricDirective.putDimensionSet(DimensionSet.of("Instance", "inst-1"));
+        metricDirective.putDimensionSet(DimensionSet.of("Region", "us-east-1"));
+        metricDirective.putDimensionSet(new DimensionSet());
+
+        String serializedMetricDirective = objectMapper.writeValueAsString(metricDirective);
+
+        assertEquals(
+                serializedMetricDirective,
+                "{\"Dimensions\":[[\"Instance\",\"Region\"],[\"Instance\"],[\"Region\"],[]],\"Metrics\":[],\"Namespace\":\"aws-embedded-metrics\"}");
     }
 
     @Test