fix: use embedded Proguard configuration instead of compile-time annotation (#1491)

* Revert "keep GoogleUtils (#1467)"

This reverts commit b70e8ef.

* Add proguard resource file to ensure GoogleUtils is kept for Android users.

* Revert "Add google android repository to Gradle instructions (#1489)"

This reverts commit 57a7bb7.

* Restore README

Author: anuraaga

google-api-client/pom.xml

@@ -145,23 +145,10 @@
       <artifactId>commons-codec</artifactId>
       <scope>provided</scope>
       <version>1.14</version>
-    </dependency>
+   </dependency>
     <dependency>
       <groupId>com.google.guava</groupId>
       <artifactId>guava</artifactId>
     </dependency>
-    <dependency>
-      <groupId>androidx.annotation</groupId>
-      <artifactId>annotation</artifactId>
-      <version>1.1.0</version>
-    </dependency>
   </dependencies>
-  
-  <repositories>  
-    <repository>
-      <id>google</id>
-      <name>Google Maven Repository</name>
-      <url>https://maven.google.com/</url>
-    </repository>
-  </repositories>
 </project>

google-api-client/src/main/java/com/google/api/client/googleapis/GoogleUtils.java

@@ -14,7 +14,6 @@
 
 package com.google.api.client.googleapis;
 
-import androidx.annotation.Keep;
 import com.google.api.client.util.SecurityUtils;
 import com.google.common.annotations.VisibleForTesting;
 import java.io.IOException;
@@ -31,7 +30,6 @@
  * @since 1.12
  * @author [email protected] (Ravi Mistry)
  */
-@Keep
 public final class GoogleUtils {
 
   /** Current release version. */

google-api-client/src/main/resources/META-INF/proguard/google-api-client.pro

@@ -0,0 +1,2 @@
+# https://github.com/googleapis/google-api-java-client/issues/1450
+-keep public class com.google.api.client.googleapis.GoogleUtils