fix(java): use body as error message APIC-541 (#734)

Author: millotp

clients/algoliasearch-client-java-2/algoliasearch-core/src/main/java/com/algolia/utils/retry/RetryOutcome.java

@@ -58,8 +58,11 @@ public Response intercept(Chain chain) throws IOException {
               response.close();
               continue;
             }
-            // unkown state, fail
-            throw new AlgoliaApiException(response.message(), response.code());
+            String message = response.message();
+            if (response.body() != null) {
+              message = response.body().string();
+            }
+            throw new AlgoliaApiException(message, response.code());
           } catch (AlgoliaApiException e) {
             throw e;
           } catch (SocketTimeoutException e) {