fix: all impacted samples

Author: pkernevez

samples/client/petstore/spring-cloud-deprecated/src/main/java/org/openapitools/model/ModelApiResponse.java

@@ -125,7 +125,7 @@ public String toString() {
    * Convert the given object to string with each line indented by 4 spaces
    * (except the first line).
    */
-  private String toIndentedString(Object o) {
+  private String toIndentedString(@Nullable Object o) {
     if (o == null) {
       return "null";
     }

samples/client/petstore/spring-cloud-deprecated/src/main/java/org/openapitools/model/Order.java

@@ -238,7 +238,7 @@ public String toString() {
    * Convert the given object to string with each line indented by 4 spaces
    * (except the first line).
    */
-  private String toIndentedString(Object o) {
+  private String toIndentedString(@Nullable Object o) {
     if (o == null) {
       return "null";
     }

samples/client/petstore/spring-cloud-deprecated/src/main/java/org/openapitools/model/Pet.java

@@ -275,7 +275,7 @@ public String toString() {
    * Convert the given object to string with each line indented by 4 spaces
    * (except the first line).
    */
-  private String toIndentedString(Object o) {
+  private String toIndentedString(@Nullable Object o) {
     if (o == null) {
       return "null";
     }

samples/client/petstore/spring-cloud-deprecated/src/main/java/org/openapitools/model/Tag.java

@@ -99,7 +99,7 @@ public String toString() {
    * Convert the given object to string with each line indented by 4 spaces
    * (except the first line).
    */
-  private String toIndentedString(Object o) {
+  private String toIndentedString(@Nullable Object o) {
     if (o == null) {
       return "null";
     }

samples/client/petstore/spring-cloud-deprecated/src/main/java/org/openapitools/model/User.java

@@ -243,7 +243,7 @@ public String toString() {
    * Convert the given object to string with each line indented by 4 spaces
    * (except the first line).
    */
-  private String toIndentedString(Object o) {
+  private String toIndentedString(@Nullable Object o) {
     if (o == null) {
       return "null";
     }

samples/client/petstore/spring-cloud-feign-without-url/src/main/java/org/openapitools/model/Category.java

@@ -100,7 +100,7 @@ public String toString() {
    * Convert the given object to string with each line indented by 4 spaces
    * (except the first line).
    */
-  private String toIndentedString(Object o) {
+  private String toIndentedString(@Nullable Object o) {
     if (o == null) {
       return "null";
     }

samples/client/petstore/spring-cloud-feign-without-url/src/main/java/org/openapitools/model/ModelApiResponse.java

@@ -126,7 +126,7 @@ public String toString() {
    * Convert the given object to string with each line indented by 4 spaces
    * (except the first line).
    */
-  private String toIndentedString(Object o) {
+  private String toIndentedString(@Nullable Object o) {
     if (o == null) {
       return "null";
     }

samples/client/petstore/spring-cloud-feign-without-url/src/main/java/org/openapitools/model/Order.java

@@ -237,7 +237,7 @@ public String toString() {
    * Convert the given object to string with each line indented by 4 spaces
    * (except the first line).
    */
-  private String toIndentedString(Object o) {
+  private String toIndentedString(@Nullable Object o) {
     if (o == null) {
       return "null";
     }

samples/client/petstore/spring-cloud-feign-without-url/src/main/java/org/openapitools/model/Pet.java

@@ -276,7 +276,7 @@ public String toString() {
    * Convert the given object to string with each line indented by 4 spaces
    * (except the first line).
    */
-  private String toIndentedString(Object o) {
+  private String toIndentedString(@Nullable Object o) {
     if (o == null) {
       return "null";
     }

samples/client/petstore/spring-cloud-feign-without-url/src/main/java/org/openapitools/model/Tag.java

@@ -100,7 +100,7 @@ public String toString() {
    * Convert the given object to string with each line indented by 4 spaces
    * (except the first line).
    */
-  private String toIndentedString(Object o) {
+  private String toIndentedString(@Nullable Object o) {
     if (o == null) {
       return "null";
     }