Add .monitoring exemption to DotPrefixValidator

This was something we were planning on removing, but have not yet.

Resolves #124131

Author: dakrone

modules/dot-prefix-validation/src/main/java/org/elasticsearch/validation/DotPrefixValidator.java

@@ -73,7 +73,8 @@ public abstract class DotPrefixValidator<RequestType> implements MappedActionFil
             "\\.ml-state-\\d+",
             "\\.slo-observability\\.sli-v\\d+.*",
             "\\.slo-observability\\.summary-v\\d+.*",
-            "\\.entities\\.v\\d+\\.latest\\..*"
+            "\\.entities\\.v\\d+\\.latest\\..*",
+            "\\.monitoring-es-8-.*"
         ),
         (patternList) -> patternList.forEach(pattern -> {
             try {

modules/dot-prefix-validation/src/test/java/org/elasticsearch/validation/DotPrefixValidatorTests.java

@@ -67,7 +67,7 @@ public void testValidation() {
 
         // Test ignored patterns
         nonOpV.validateIndices(Set.of(".ml-state-21309"));
-        nonOpV.validateIndices(Set.of(">.ml-state-21309>"));
+        nonOpV.validateIndices(Set.of("<.ml-state-21309>"));
         nonOpV.validateIndices(Set.of(".slo-observability.sli-v2"));
         nonOpV.validateIndices(Set.of(".slo-observability.sli-v2.3"));
         nonOpV.validateIndices(Set.of(".slo-observability.sli-v2.3-2024-01-01"));
@@ -79,6 +79,8 @@ public void testValidation() {
         nonOpV.validateIndices(Set.of(".entities.v1.latest.builtin_services_from_ecs_data"));
         nonOpV.validateIndices(Set.of(".entities.v92.latest.eggplant.potato"));
         nonOpV.validateIndices(Set.of("<.entities.v12.latest.eggplant-{M{yyyy-MM-dd|UTC}}>"));
+        nonOpV.validateIndices(Set.of(".monitoring-es-8-thing"));
+        nonOpV.validateIndices(Set.of("<.monitoring-es-8-thing>"));
 
         // Test pattern added to the settings
         nonOpV.validateIndices(Set.of(".potato5"));