update migration guide

Author: scotthart

doc/v3-migration-guide.md

@@ -42,6 +42,23 @@ module which can be added to your `MODULE.bazel` file as a dependency.
 
 ### CMake
 
+<details>
+<summary>Removed backward compatible proto interface libraries.</summary>
+
+If your application links directly to one of these decommissioned proto
+libraries, the CMakeLists.txt should be updated with the preferred proto library
+name.
+
+| Library                    | Decommissioned Proto Library        | Preferred Proto Library                |
+| -------------------------- | ----------------------------------- | -------------------------------------- |
+| google/cloud/dialogflow_es | cloud_dialogflow_v2_protos          | google-cloud-cpp::dialogflow_es_protos |
+| google/cloud/logging       | logging_type_type_protos            | google-cloud-cpp::logging_protos       |
+| google/cloud/speech        | cloud_speech_protos                 | google-cloud-cpp::speech_protos        |
+| google/cloud/texttospeech  | cloud_texttospeech_protos           | google-cloud-cpp::texttospeech_protos  |
+| google/cloud/trace         | devtools_cloudtrace_v2_trace_protos | google-cloud-cpp::trace_protos         |
+
+</details>
+
 ### Common
 
 <details>
@@ -487,6 +504,122 @@ internal legacy files.
 
 </details>
 
+<details>
+<summary>Removed <code>bigtable::AdminClient</code> and <code>bigtable::TableAdmin</code></summary>
+
+The `bigtable::AdminClient` class and `bigtable::TableAdmin` class have been
+replaced with `bigtable_admin::BigtableTableAdminClient`.
+
+**Before:**
+
+```cpp
+
+std::shared_ptr<bigtable::AdminClient> admin_client = 
+    bigtable::MakeAdminClient("project-id");
+auto table_admin = std::make_unique<bigtable::TableAdmin>(
+    admin_client, "instance-id");
+
+// Drop a selection of rows by key prefix.
+auto result = table_admin.DropRowByPrefix("table-id", "row-key-prefix");
+
+// Drop all rows.
+result = table_admin.DropAllRows("table-id");
+```
+
+**After:**
+
+```cpp
+#include "google/cloud/bigtable/admin/bigtable_table_admin_client.h"
+
+auto table_admin = bigtable_admin::BigtableTableAdminClient(
+    bigtable_admin::MakeBigtableAdminConnection());
+auto table_name = bigtable::TableName("project-id", "instance-id", "table-id");
+
+// Drop a selection of rows by key prefix.
+google::bigtable::admin::v2::DropRowRangeRequest drop_rows_by_prefix;
+drop_rows_by_prefix.set_name(table_name);
+drop_rows_by_prefix.set_row_key_prefix("row-key-prefix");
+auto result = table_admin.DropRowRange(drop_rows_by_prefix);
+
+// Drop all rows.
+google::bigtable::admin::v2::DropRowRangeRequest drop_all_rows;
+drop_all_rows.set_name(table_name);
+drop_all_rows.set_delete_all_data_from_table(true);
+result = table_admin.DropRowRange(drop_all_rows);
+```
+
+</details>
+
+<details><summary><code>WaitForConsistency</code> is now a free function</summary>
+
+With the removal of the `bigtable::TableAdmin` class, `WaitForConsistency` has
+been moved to `bigtable_admin::BigtableTableAdminClient::WaitForConsistency`.
+
+**Before:**
+
+```cpp
+
+std::shared_ptr<bigtable::AdminClient> admin_client = 
+    bigtable::MakeAdminClient("project-id");
+auto table_admin = std::make_unique<bigtable::TableAdmin>(
+    admin_client, "instance-id");
+
+auto token = table_admin.GenerateConsistencyToken("table-id");
+if (!token) throw std::runtime_error(token.status().message());
+auto result = table_admin.WaitForConsistency("table-id", *token);
+```
+
+**After:**
+
+```cpp
+#include "google/cloud/bigtable/admin/bigtable_table_admin_client.h"
+
+auto connection = bigtable_admin::MakeBigtableAdminConnection();
+auto table_admin = bigtable_admin::BigtableTableAdminClient(connection);
+auto table_name = bigtable::TableName("project-id", "instance-id", "table-id");
+
+auto token = table_admin.GenerateConsistencyToken(table_name);
+if (!token) throw std::runtime_error(token.status().message());
+
+google::bigtable::admin::v2::CheckConsistencyRequest wait_request;
+wait_request.set_name(table_name);
+wait_request.set_consistency_token(token->consistency_token());
+auto wait_response = table_admin.WaitForConsistency(wait_request).get();
+```
+
+</details>
+
+<details>
+<summary>Removed <code>bigtable::InstanceAdminClient</code> and <code>bigtable::InstanceAdmin</code></summary>
+
+The `bigtable::InstanceAdminClient` class and `bigtable::InstanceAdmin` class
+have been replaced with `bigtable_admin::BigtableInstanceAdminClient`.
+
+**Before:**
+
+```cpp
+auto instance_admin_client = bigtable::MakeInstanceAdminClient("project-id");
+auto instance_admin =
+    std::make_unique<bigtable::InstanceAdmin>(instance_admin_client);
+
+auto clusters = instance_admin->ListClusters();
+```
+
+**After:**
+
+```cpp
+#include "google/cloud/bigtable/admin/bigtable_instance_admin_client.h"
+
+auto instance_admin =
+        std::make_unique<bigtable_admin::BigtableInstanceAdminClient>(
+            bigtable_admin::MakeBigtableInstanceAdminConnection());
+
+auto clusters = instance_admin->ListClusters(
+    InstanceName("project-id", "instance-id"));
+```
+
+</details>
+
 ### Pubsub
 
 <details>
@@ -936,6 +1069,35 @@ void UseRawClient(google::cloud::storage::Client client) {
 
 </details>
 
+<details>
+<summary>Removed <code>storage_experimental::GrpcPluginOption</code> and <code>storage_experimental::DefaultGrpcClient</code></summary>
+
+The `storage_experimental::GrpcPluginOption` is no longer necessary. Instead of
+calling `storage_experimental::DefaultGrpcClient` now call
+`storage::MakeGrpcClient`
+
+**Before:**
+
+```cpp
+#include "google/cloud/storage/grpc_plugin.h"
+namespace gc = ::google::cloud;
+
+auto options = gc::Options{}
+    .set<gc::storage_experimental::GrpcPluginOption>("media");
+auto client = gc::storage_experimental::DefaultGrpcClient(options);
+```
+
+**After:**
+
+```cpp
+#include "google/cloud/storage/grpc_plugin.h"
+namespace gc = ::google::cloud;
+
+auto client = gc::storage::MakeGrpcClient();
+```
+
+</details>
+
 <details>
 <summary>Removed deprecated <code>Oauth2CredentialsOption</code></summary>