Update AppSearchManager class header with description and examples

import java.util.function.Consumer;

/**

 * This class provides access to the centralized AppSearch index maintained by the system.

 * Provides access to the centralized AppSearch index maintained by the system.

 *

 * <p>Apps can index structured text documents with AppSearch, which can then be retrieved through

 * the query API.

 * <p>AppSearch is a search library for managing structured data featuring:

 * <ul>

 *     <li>A fully offline on-device solution

 *     <li>A set of APIs for applications to index documents and retrieve them via full-text search

 *     <li>APIs for applications to allow the System to display their content on system UI surfaces

 *     <li>Similarly, APIs for applications to allow the System to share their content with other

 *     specified applications.

 * </ul>

 *

 * <p>Applications create a database by opening an {@link AppSearchSession}.

 *

 * <p>Example:

 * <pre>

 * AppSearchManager appSearchManager = context.getSystemService(AppSearchManager.class);

 *

 * AppSearchManager.SearchContext searchContext = new AppSearchManager.SearchContext.Builder().

 *    setDatabaseName(dbName).build());

 * appSearchManager.createSearchSession(searchContext, mExecutor, appSearchSessionResult -> {

 *      mAppSearchSession = appSearchSessionResult.getResultValue();

 * });</pre>

 *

 * <p>After opening the session, a schema must be set in order to define the organizational

 * structure of data. The schema is set by calling {@link AppSearchSession#setSchema}. The schema

 * is composed of a collection of {@link AppSearchSchema} objects, each of which defines a unique

 * type of data.

 *

 * <p>Example:

 * <pre>

 * AppSearchSchema emailSchemaType = new AppSearchSchema.Builder("Email")

 *     .addProperty(new StringPropertyConfig.Builder("subject")

 *        .setCardinality(PropertyConfig.CARDINALITY_OPTIONAL)

 *        .setIndexingType(PropertyConfig.INDEXING_TYPE_PREFIXES)

 *        .setTokenizerType(PropertyConfig.TOKENIZER_TYPE_PLAIN)

 *    .build()

 * ).build();

 *

 * SetSchemaRequest request = new SetSchemaRequest.Builder().addSchema(emailSchemaType).build();

 * mAppSearchSession.set(request, mExecutor, appSearchResult -> {

 *      if (appSearchResult.isSuccess()) {

 *           //Schema has been successfully set.

 *      }

 * });</pre>

 *

 * <p>The basic unit of data in AppSearch is represented as a {@link GenericDocument} object,

 * containing a URI, namespace, time-to-live, score, and properties. A namespace organizes a

 * logical group of documents. For example, a namespace can be created to group documents on a

 * per-account basis. A URI identifies a single document within a namespace. The combination

 * of URI and namespace uniquely identifies a {@link GenericDocument} in the database.

 *

 * <p>Once the schema has been set, {@link GenericDocument} objects can be put into the database

 * and indexed by calling {@link AppSearchSession#put}.

 *

 * <p>Example:

 * <pre>

 * // Although for this example we use GenericDocument directly, we recommend extending

 * // GenericDocument to create specific types (i.e. Email) with specific setters/getters.

 * GenericDocument email = new GenericDocument.Builder<>(URI, EMAIL_SCHEMA_TYPE)

 *     .setNamespace(NAMESPACE)

 *     .setPropertyString(“subject”, EMAIL_SUBJECT)

 *     .setScore(EMAIL_SCORE)

 *     .build();

 *

 * PutDocumentsRequest request = new PutDocumentsRequest.Builder().addGenericDocuments(email)

 *     .build();

 * mAppSearchSession.put(request, mExecutor, appSearchBatchResult -> {

 *      if (appSearchBatchResult.isSuccess()) {

 *           //All documents have been successfully indexed.

 *      }

 * });</pre>

 *

 * <p>Searching within the database is done by calling {@link AppSearchSession#search} and providing

 * the query string to search for, as well as a {@link SearchSpec}.

 *

 * <p>Alternatively, {@link AppSearchSession#getByUri} can be called to retrieve documents by URI

 * and namespace.

 *

 * <p>Document removal is done either by time-to-live expiration, or explicitly calling a remove

 * operation. Remove operations can be done by URI and namespace via

 * {@link AppSearchSession#remove(RemoveByUriRequest, Executor, BatchResultCallback)},

 * or by query via {@link AppSearchSession#remove(String, SearchSpec, Executor, Consumer)}.

 */

// TODO(b/148046169): This class header needs a detailed example/tutorial.

@SystemService(Context.APP_SEARCH_SERVICE)

public class AppSearchManager {

    /**