docs(client): update client-side adoption guides and README for generator cleanup

- Updated client-side adoption documentation with Spotless plugin integration
  and `.openapi-generator-ignore` rules for redundant DTO cleanup.
- Revised customer-service-client README.md to include ignore patterns section.
- Ensured consistency between client-side build setup and actual generator behavior.

Author: bsayli

customer-service-client/README.md

@@ -252,6 +252,22 @@ try {
 
 ---
 
+### 🧹 Ignoring Redundant Generated DTOs
+
+The following patterns in [`.openapi-generator-ignore`](.openapi-generator-ignore) prevent redundant DTOs from being regenerated.
+These classes already exist in the shared `common` package and are excluded from code generation.
+
+```bash
+# --- Custom additions for generated DTO cleanup ---
+**/src/gen/java/**/generated/dto/Page*.java
+**/src/gen/java/**/generated/dto/ServiceResponse.java
+**/src/gen/java/**/generated/dto/ServiceResponseVoid.java
+**/src/gen/java/**/generated/dto/Meta.java
+**/src/gen/java/**/generated/dto/Sort.java
+```
+
+---
+
 ## 📚 Notes
 
 * **Toolchain:** Java 21, Spring Boot 3.4.10, OpenAPI Generator 7.16.0

docs/adoption/client-side-adoption-pom.md

@@ -72,6 +72,10 @@ Define reusable properties to simplify plugin management and template resolution
     <openapi.generator.version>7.16.0</openapi.generator.version>
     <openapi.templates.upstream>${project.build.directory}/openapi-templates-upstream</openapi.templates.upstream>
     <openapi.templates.effective>${project.build.directory}/openapi-templates-effective</openapi.templates.effective>
+    <build.helper.plugin.version>3.6.0</build.helper.plugin.version>
+    <maven.resources.plugin.version>3.3.1</maven.resources.plugin.version>
+    <maven.dependency.plugin.version>3.8.1</maven.dependency.plugin.version>
+    <spotless-maven-plugin.version>3.0.0</spotless-maven-plugin.version>
 </properties>
 ```
 
@@ -195,8 +199,9 @@ These plugins work in sequence to **unpack, overlay, and compile** OpenAPI templ
                         </configOptions>
 
                         <additionalProperties>
-                            <commonPackage>commonPackage=your.base.openapi.client.common</commonPackage>
+                            <additionalProperty>commonPackage=your.base.openapi.client.common</additionalProperty>
                         </additionalProperties>
+                        <ignoreFileOverride>${project.basedir}/.openapi-generator-ignore</ignoreFileOverride>
                     </configuration>
                 </execution>
             </executions>
@@ -221,6 +226,35 @@ These plugins work in sequence to **unpack, overlay, and compile** OpenAPI templ
                 </execution>
             </executions>
         </plugin>
+
+        <!-- 5️⃣ Clean up generated imports (Spotless) -->
+        
+        <plugin>
+            <groupId>com.diffplug.spotless</groupId>
+            <artifactId>spotless-maven-plugin</artifactId>
+            <version>${spotless-maven-plugin.version}</version>
+
+            <configuration>
+                <java>
+                    <includes>
+                        <include>target/generated-sources/openapi/src/gen/java/**/*.java</include>
+                    </includes>
+                    <removeUnusedImports>
+                        <engine>cleanthat-javaparser-unnecessaryimport</engine>
+                    </removeUnusedImports>
+                </java>
+            </configuration>
+            <executions>
+                <execution>
+                    <id>spotless-apply-generated</id>
+                    <phase>process-sources</phase>
+                    <goals>
+                        <goal>apply</goal>
+                    </goals>
+                </execution>
+            </executions>
+        </plugin>
+        
     </plugins>
 </build>
 ```
@@ -235,6 +269,7 @@ These plugins work in sequence to **unpack, overlay, and compile** OpenAPI templ
 | **maven-resources-plugin**         | Overlays your local Mustache templates on top of upstream ones.  |
 | **openapi-generator-maven-plugin** | Generates type-safe client code using the effective templates.   |
 | **build-helper-maven-plugin**      | Ensures generated sources are included in the compilation phase. |
+| **spotless-maven-plugin**          | Automatically removes unused imports and keeps generated sources clean. |
 
 Together, these guarantee your **generics‑aware response wrappers** (e.g., `ServiceClientResponse<T>`) are generated
 cleanly and consistently across builds.

docs/adoption/client-side-adoption.md

@@ -61,6 +61,34 @@ new `{ data, meta }` response structure and RFC 9457 `ProblemDetail` error model
 
 ---
 
+### 🧹 Ignoring Redundant Generated DTOs
+
+To prevent OpenAPI Generator from re-creating DTOs that already exist in the shared `common` package,
+add the following patterns to your `.openapi-generator-ignore` file.
+This avoids redundant model generation (e.g., `Page`, `Meta`, `Sort`, `ServiceResponse`) and keeps diffs minimal.
+
+```bash
+# --- Custom additions for generated DTO cleanup ---
+**/src/gen/java/**/generated/dto/Page*.java
+**/src/gen/java/**/generated/dto/ServiceResponse.java
+**/src/gen/java/**/generated/dto/ServiceResponseVoid.java
+**/src/gen/java/**/generated/dto/Meta.java
+**/src/gen/java/**/generated/dto/Sort.java
+```
+
+> **Note:**
+> The paths above assume your `openapi-generator-maven-plugin` uses
+> `sourceFolder=src/gen/java`.
+> If your configuration differs, adjust the directory prefix accordingly.
+>
+> Also make sure your POM specifies the file override:
+>
+> ```xml
+> <ignoreFileOverride>${project.basedir}/.openapi-generator-ignore</ignoreFileOverride>
+> ```
+
+---
+
 ## 🧩 Core Classes (Shared Base)
 
 Copy these into your client module under `openapi/client/common`: