feat: support creating shaded jars (#333)

Some applications that load multiple JDBC drivers may run into dependency
conflicts if other JDBC drivers use the same dependencies but different
versions. This problem can be mitigated by creating a jar with shaded
dependencies. This change adds a Maven profile for creating shaded jars.

Fixes #316

.readme-partials.yaml

@@ -23,3 +23,14 @@ custom_content: |
      }
    }
    ```
+   
+   ### Creating a Shaded Jar
+   
+   A jar with all dependencies included is automatically generated when you execute `mvn package`.
+   The dependencies in this jar are not shaded. To create a jar with shaded dependencies you must
+   activate the `shade` profile like this:
+   
+    ```
+    mvn package -Pshade
+    ```
+   

pom.xml

@@ -309,6 +309,50 @@
       </plugins>
     </pluginManagement>
   </build>
+
+  <profiles>
+    <profile>
+      <id>shade</id>
+      <build>
+        <plugins>
+          <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-shade-plugin</artifactId>
+            <configuration>
+              <relocations>
+                <relocation>
+                  <pattern>com</pattern>
+                  <shadedPattern>com.google.cloud.spanner.jdbc.shaded.com</shadedPattern>
+                  <excludes>
+                    <exclude>com.google.cloud.spanner.**</exclude>
+                  </excludes>
+                </relocation>
+                <relocation>
+                  <pattern>android</pattern>
+                  <shadedPattern>com.google.cloud.spanner.jdbc.shaded.android</shadedPattern>
+                </relocation>
+                <relocation>
+                  <pattern>io</pattern>
+                  <shadedPattern>com.google.cloud.spanner.jdbc.shaded.io</shadedPattern>
+                  <excludes>
+                    <exclude>io.grpc.netty.shaded.**</exclude>
+                  </excludes>
+                </relocation>
+                <relocation>
+                  <pattern>org</pattern>
+                  <shadedPattern>com.google.cloud.spanner.jdbc.shaded.org</shadedPattern>
+                  <excludes>
+                    <exclude>org.conscrypt.**</exclude>
+                  </excludes>
+                </relocation>
+              </relocations>
+            </configuration>
+          </plugin>
+        </plugins>
+      </build>
+    </profile>
+  </profiles>
+
   <reporting>
     <plugins>
       <plugin>