[JAVA][RETROFIT2] Include java.util.Set in fullJavaUtil imports (#14048)

* Include java.util.Set in fullJavaUtil imports

* Update java-retrofit2 samples

modules/openapi-generator/src/main/resources/Java/libraries/retrofit2/api.mustache

@@ -33,6 +33,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 {{/fullJavaUtil}}
 
 {{#operations}}

samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/api/AnotherFakeApi.java

@@ -15,6 +15,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface AnotherFakeApi {
   /**

samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/api/FakeApi.java

@@ -23,6 +23,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface FakeApi {
   /**

samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/api/FakeClassnameTags123Api.java

@@ -15,6 +15,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface FakeClassnameTags123Api {
   /**

samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/api/PetApi.java

@@ -18,6 +18,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface PetApi {
   /**

samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/api/StoreApi.java

@@ -15,6 +15,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface StoreApi {
   /**

samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/api/UserApi.java

@@ -16,6 +16,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface UserApi {
   /**

samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/api/AnotherFakeApi.java

@@ -16,6 +16,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface AnotherFakeApi {
   /**

samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/api/FakeApi.java

@@ -24,6 +24,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface FakeApi {
   /**

samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/api/FakeClassnameTags123Api.java

@@ -16,6 +16,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface FakeClassnameTags123Api {
   /**

samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/api/PetApi.java

@@ -19,6 +19,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface PetApi {
   /**

samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/api/StoreApi.java

@@ -16,6 +16,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface StoreApi {
   /**

samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/api/UserApi.java

@@ -17,6 +17,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface UserApi {
   /**

samples/client/petstore/java/retrofit2rx3/src/main/java/org/openapitools/client/api/AnotherFakeApi.java

@@ -16,6 +16,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface AnotherFakeApi {
   /**

samples/client/petstore/java/retrofit2rx3/src/main/java/org/openapitools/client/api/FakeApi.java

@@ -24,6 +24,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface FakeApi {
   /**

samples/client/petstore/java/retrofit2rx3/src/main/java/org/openapitools/client/api/FakeClassnameTags123Api.java

@@ -16,6 +16,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface FakeClassnameTags123Api {
   /**

samples/client/petstore/java/retrofit2rx3/src/main/java/org/openapitools/client/api/PetApi.java

@@ -19,6 +19,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface PetApi {
   /**

samples/client/petstore/java/retrofit2rx3/src/main/java/org/openapitools/client/api/StoreApi.java

@@ -16,6 +16,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface StoreApi {
   /**

samples/client/petstore/java/retrofit2rx3/src/main/java/org/openapitools/client/api/UserApi.java

@@ -17,6 +17,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public interface UserApi {
   /**