add packageinfo

Signed-off-by: Karen Xu <[email protected]>

Author: karenyrx

modules/transport-grpc/spi/src/main/java/org/opensearch/transport/grpc/spi/package-info.java

@@ -0,0 +1,34 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+/**
+ * Service Provider Interface (SPI) for extending gRPC transport query conversion capabilities.
+ * <p>
+ * This package provides the core interfaces and registry for implementing custom query converters
+ * that can transform protobuf query messages into OpenSearch QueryBuilder objects. External plugins
+ * can implement the {@link org.opensearch.transport.grpc.spi.QueryBuilderProtoConverter} interface
+ * to add support for custom query types in gRPC requests.
+ * </p>
+ * <p>
+ * The SPI mechanism leverages OpenSearch's {@code ExtensiblePlugin} framework, which internally
+ * uses Java's {@code ServiceLoader} for discovery. Plugins must:
+ * </p>
+ * <ul>
+ *   <li>Implement {@link org.opensearch.transport.grpc.spi.QueryBuilderProtoConverter}</li>
+ *   <li>Return the converter instance from their plugin's {@code createComponents()} method</li>
+ *   <li>Create a {@code META-INF/services} file listing their converter implementation</li>
+ *   <li>Declare {@code transport-grpc} in their plugin descriptor's {@code extended.plugins} list</li>
+ * </ul>
+ * <p>
+ * For converters that need to handle nested queries (e.g., filter clauses), the registry injection
+ * pattern allows access to built-in converters for standard query types like MatchAll, Term, and Terms.
+ * </p>
+ *
+ * @since 3.2.0
+ */
+package org.opensearch.transport.grpc.spi;