Add a dependency on AutoValue to simplify handling of value classes. (#471)

## What changes are proposed in this pull request?

This PR adds a dependency on [Google's AutoValue
library](https://chromium.googlesource.com/external/github.com/google/auto/+/refs/tags/auto-value-1.6.2/value/userguide/index.md)
to simplify the development and maintenance of value classes. See [Why
should I use
AutoValue?](https://chromium.googlesource.com/external/github.com/google/auto/+/refs/tags/auto-value-1.6.2/value/userguide/why.md)
for more details.

The decision to use AutoValue is motivated by the fact that the
Databricks SDK must support Java 8 for the foreseeable future and does
not have access to new language features such as records — which would
obsolete AutoValue.

NO_CHANGELOG=true

## How is this tested?

Simplified one small internal class to use AutoValue and validated that
the impacted unit and integration tests are fine with it.

Author: renaudhartert-db

databricks-sdk-java/pom.xml

@@ -103,5 +103,18 @@
       <artifactId>jackson-datatype-jsr310</artifactId>
       <version>${jackson.version}</version>
     </dependency>
+    <!-- Google Auto Value -->
+    <dependency>
+      <groupId>com.google.auto.value</groupId>
+      <artifactId>auto-value</artifactId>
+      <version>1.10.4</version>
+      <scope>provided</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.google.auto.value</groupId>
+      <artifactId>auto-value-annotations</artifactId>
+      <version>1.10.4</version>
+      <scope>provided</scope>
+    </dependency>
   </dependencies>
 </project>

databricks-sdk-java/src/main/java/com/databricks/sdk/core/oauth/DataPlaneTokenSource.java

@@ -1,6 +1,7 @@
 package com.databricks.sdk.core.oauth;
 
 import com.databricks.sdk.core.http.HttpClient;
+import com.google.auto.value.AutoValue;
 import java.util.Objects;
 import java.util.concurrent.ConcurrentHashMap;
 
@@ -17,44 +18,19 @@ public class DataPlaneTokenSource {
   private final TokenSource cpTokenSource;
   private final String host;
   private final ConcurrentHashMap<TokenSourceKey, EndpointTokenSource> sourcesCache;
+
   /**
    * Caching key for {@link EndpointTokenSource}, based on endpoint and authorization details. This
    * is a value object that uniquely identifies a token source configuration.
    */
-  private static final class TokenSourceKey {
-    /** The target service endpoint URL. */
-    private final String endpoint;
-
-    /** Specific authorization details for the endpoint. */
-    private final String authDetails;
+  @AutoValue
+  abstract static class TokenSourceKey {
+    abstract String endpoint();
 
-    /**
-     * Constructs a TokenSourceKey.
-     *
-     * @param endpoint The target service endpoint URL.
-     * @param authDetails Specific authorization details.
-     */
-    public TokenSourceKey(String endpoint, String authDetails) {
-      this.endpoint = endpoint;
-      this.authDetails = authDetails;
-    }
-
-    @Override
-    public boolean equals(Object o) {
-      if (this == o) {
-        return true;
-      }
-      if (o == null || getClass() != o.getClass()) {
-        return false;
-      }
-      TokenSourceKey that = (TokenSourceKey) o;
-      return Objects.equals(endpoint, that.endpoint)
-          && Objects.equals(authDetails, that.authDetails);
-    }
+    abstract String authDetails();
 
-    @Override
-    public int hashCode() {
-      return Objects.hash(endpoint, authDetails);
+    static TokenSourceKey create(String endpoint, String authDetails) {
+      return new AutoValue_DataPlaneTokenSource_TokenSourceKey(endpoint, authDetails);
     }
   }
 
@@ -101,14 +77,14 @@ public Token getToken(String endpoint, String authDetails) {
       throw new IllegalArgumentException("Authorization details cannot be empty");
     }
 
-    TokenSourceKey key = new TokenSourceKey(endpoint, authDetails);
+    TokenSourceKey key = TokenSourceKey.create(endpoint, authDetails);
 
     EndpointTokenSource specificSource =
         sourcesCache.computeIfAbsent(
             key,
             k ->
                 new EndpointTokenSource(
-                    this.cpTokenSource, k.authDetails, this.httpClient, this.host));
+                    this.cpTokenSource, k.authDetails(), this.httpClient, this.host));
 
     return specificSource.getToken();
   }

pom.xml

@@ -67,6 +67,13 @@
         <configuration>
           <source>8</source>
           <target>8</target>
+          <annotationProcessorPaths>
+            <path>
+              <groupId>com.google.auto.value</groupId>
+              <artifactId>auto-value</artifactId>
+              <version>1.10.4</version>
+            </path>
+          </annotationProcessorPaths>
         </configuration>
       </plugin>
       <plugin>