declarative config metrics delta

Author: SylvainJuge

custom/src/main/resources/co/elastic/otel/config.yaml

@@ -47,10 +47,12 @@ meter_provider:
           otlp_http:
             endpoint: ${OTEL_EXPORTER_OTLP_ENDPOINT:-http://localhost:4318}/v1/metrics
             headers_list: ${OTEL_EXPORTER_OTLP_HEADERS}
+            temporality_preference: delta
           # use the following for grpc
           # otlp_grpc:
           #  endpoint: ${OTEL_EXPORTER_OTLP_ENDPOINT}
           #  headers_list: ${OTEL_EXPORTER_OTLP_HEADERS}
+          #  temporality_preference: delta
 
 logger_provider:
   processors:

custom/src/test/java/co/elastic/otel/declarativeconfig/DefaultDeclarativeConfigTest.java

@@ -78,7 +78,8 @@ void testDefaults() {
           assertThatJson(json(config.getMeterProvider().getReaders().get(0)))
               .inPath("periodic.exporter.otlp_http")
               .isObject()
-              .containsEntry("endpoint", "http://localhost:4318/v1/metrics");
+              .containsEntry("endpoint", "http://localhost:4318/v1/metrics")
+              .containsEntry("temporality_preference", "delta");
 
           assertThat(config.getLoggerProvider()).isNotNull();
           assertThat(config.getLoggerProvider().getProcessors()).hasSize(1);