Upgrade maven-gpg-plugin to 3.2.7 with loopback pinentry

Fixes 'Inappropriate ioctl for device' error in CI environments.
The old 1.6 version doesn't support non-interactive GPG signing.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: drewnoakes

.gitignore

@@ -12,3 +12,4 @@
 build
 .DS_Store
 .gradle
+.flattened-pom.xml

pom.xml

@@ -176,14 +176,20 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-gpg-plugin</artifactId>
-                <version>1.6</version>
+                <version>3.2.7</version>
                 <executions>
                     <execution>
                         <id>sign-artifacts</id>
                         <phase>verify</phase>
                         <goals>
                             <goal>sign</goal>
                         </goals>
+                        <configuration>
+                            <gpgArguments>
+                                <arg>--pinentry-mode</arg>
+                                <arg>loopback</arg>
+                            </gpgArguments>
+                        </configuration>
                     </execution>
                 </executions>
             </plugin>