feat: Introduce Cloud Translation V3 client (#2366)

* add synth script

* generate translate v3 client

* update README

* update composer files

* update docs site

* update test group name

* add to the README

Translate/README.md

@@ -36,7 +36,7 @@ $ composer require google/cloud
 Please see our [Authentication guide](https://github.com/googleapis/google-cloud-php/blob/master/AUTHENTICATION.md) for more information
 on authenticating your client. Once authenticated, you'll be ready to start making requests.
 
-### Sample
+### Sample Using the Handwritten Client (Interacts with the V2 API)
 
 ```php
 require 'vendor/autoload.php';
@@ -77,6 +77,41 @@ foreach ($languages as $language) {
 }
 ```
 
+### Sample Using the Generated Client (Interacts with the V3 API)
+
+```php
+require 'vendor/autoload.php';
+
+use Google\Cloud\Translate\V3\TranslationServiceClient;
+
+$translationClient = new TranslationServiceClient();
+$content = ['one', 'two', 'three'];
+$targetLanguage = 'es';
+$response = $translationClient->translateText(
+    $content,
+    $targetLanguage,
+    TranslationServiceClient::locationName('[PROJECT_ID]', 'global')
+);
+
+foreach ($response->getTranslations() as $key => $translation) {
+    $separator = $key === 2
+        ? '!'
+        : ', ';
+    echo $translation->getTranslatedText() . $separator;
+}
+```
+
+### Choosing the Right Client for You
+
+This component offers both a handwritten and generated client, used to access the V2 and V3 translation APIs, respectively.
+Both clients will receive on-going support and feature additions, however, it is worth noting the streamlined nature of
+the generated client means it will receive updates more frequently. Additionally, the generated client is capable of
+utilizing gRPC for its transport (by installing the gRPC extension) while the handwritten client interacts over
+REST & HTTP/1.1 only.
+
+The handwritten client can be found under `Google\Cloud\Translate\TranslateClient`, whereas the generated client is
+found under `Google\Cloud\Translate\V3\TranslationServiceClient`.
+
 ### Version
 
 This component is considered GA (generally available). As such, it will not introduce backwards-incompatible changes in

Translate/composer.json

@@ -4,14 +4,19 @@
     "license": "Apache-2.0",
     "minimum-stability": "stable",
     "require": {
-        "google/cloud-core": "^1.32"
+        "google/cloud-core": "^1.32",
+        "google/gax": "^1.1"
     },
      "require-dev": {
         "phpunit/phpunit": "^4.8|^5.0",
         "squizlabs/php_codesniffer": "2.*",
         "phpdocumentor/reflection": "^3.0",
         "erusev/parsedown": "^1.6"
     },
+    "suggest": {
+        "ext-grpc": "The gRPC extension enables use of the performant gRPC transport",
+        "ext-protobuf": "Provides a significant increase in throughput over the pure PHP protobuf implementation. See https://cloud.google.com/php/grpc for installation instructions."
+    },
     "extra": {
         "component": {
             "id": "cloud-translate",
@@ -22,7 +27,8 @@
     },
     "autoload": {
         "psr-4": {
-            "Google\\Cloud\\Translate\\": "src"
+            "Google\\Cloud\\Translate\\": "src",
+            "GPBMetadata\\Google\\Cloud\\Translate\\": "metadata"
         }
     },
     "autoload-dev": {