fix: add one more method in multipartbuilder to build from json

Author: mrasif

imagekit-sdk/build.gradle

@@ -16,4 +16,5 @@ dependencies {
     compile fileTree(include: ['*.jar'], dir: '../libs')
     testCompile group: 'junit', name: 'junit', version: '4.12'
     testCompile "org.mockito:mockito-all:2.+"
+    testImplementation 'com.squareup.okhttp3:mockwebserver:3.10.0'
 }

imagekit-sdk/src/main/java/io/imagekit/sdk/tasks/MultipartBuilder.java

@@ -64,4 +64,13 @@ public RequestBody build(FileUpdateRequest fileUpdateRequest){
         }
         return RequestBody.create(MediaType.parse("application/json; charset=utf-8"), new Gson().toJson(fileUpdateRequest));
     }
+
+    public RequestBody build(String json){
+        if (json==null){
+            throw new RuntimeException("Error: You can't send null body.");
+        }
+        else {
+            return RequestBody.create(MediaType.parse("application/json; charset=utf-8"), json);
+        }
+    }
 }

imagekit-sdk/src/main/java/io/imagekit/sdk/tasks/RestClient.java

@@ -334,7 +334,7 @@ public ResultFileDelete bulkDeleteFiles(List<String> fileIds){
         request=new Request.Builder()
                 .url(url)
                 .post(
-                    RequestBody.create(MediaType.parse("application/json; charset=utf-8"), String.format("{\"fileIds\":%s}",new Gson().toJson(fileIds)))
+                        multipartBuilder.build(String.format("{\"fileIds\":%s}",new Gson().toJson(fileIds)))
                 )
                 .headers(Headers.of(headers))
                 .build();
@@ -380,7 +380,7 @@ public ResultCache purgeCache(String url){
         request=new Request.Builder()
                 .url("https://api.imagekit.io/v1/files/purge")
                 .post(
-                        RequestBody.create(MediaType.parse("application/json; charset=utf-8"), String.format("{\"url\":\"%s\"}",url))
+                        multipartBuilder.build(String.format("{\"url\":\"%s\"}",url))
                 )
                 .headers(Headers.of(headers))
                 .build();