Use custom MongodbContext instead of generic SenderContext

Observations were created with Micrometer's generic SenderContext, preventing users from filtering or customizing MongoDB observations
by context type. This blocks the ObservationConvention pattern that Spring Boot needs for tag alignment.
Introduced MongodbContext extending SenderContext<Object> with Kind.CLIENT, giving users a MongoDB-specific type
to register ObservationHandler<MongodbContext> or ObservationConvention<MongodbContext>
instances scoped to only MongoDB observations.

Author: nhachicha

driver-core/src/main/com/mongodb/internal/observability/micrometer/MicrometerTracer.java

@@ -22,8 +22,6 @@
 import io.micrometer.common.KeyValues;
 import io.micrometer.observation.Observation;
 import io.micrometer.observation.ObservationRegistry;
-import io.micrometer.observation.transport.Kind;
-import io.micrometer.observation.transport.SenderContext;
 import org.bson.BsonDocument;
 import org.bson.BsonReader;
 import org.bson.json.JsonMode;
@@ -96,8 +94,7 @@ public boolean includeCommandPayload() {
     }
 
     private Observation getObservation(final MongodbObservation observationType, final String name) {
-        return observationType.observation(observationRegistry,
-                        () -> new SenderContext<>((carrier, key, value) -> {}, Kind.CLIENT))
+        return observationType.observation(observationRegistry, MongodbContext::new)
                 .contextualName(name);
     }
     /**

driver-core/src/main/com/mongodb/internal/observability/micrometer/MongodbContext.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2008-present MongoDB, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.mongodb.internal.observability.micrometer;
+
+import io.micrometer.observation.transport.Kind;
+import io.micrometer.observation.transport.SenderContext;
+
+/**
+ * A MongoDB-specific {@link SenderContext} for Micrometer observations.
+ * <p>
+ * Extends {@link SenderContext} with {@link Kind#CLIENT} to preserve the client span kind
+ * in the tracing bridge. Provides a MongoDB-specific type that users can filter on
+ * when registering {@code ObservationHandler} or {@code ObservationConvention} instances.
+ * </p>
+ *
+ * @since 5.7
+ */
+public class MongodbContext extends SenderContext<Object> {
+    public MongodbContext() {
+        super((carrier, key, value) -> { }, Kind.CLIENT);
+    }
+}